Belief is a whole. One who believes in all of the six pillars of belief is called a believer. Anybody who does not believe in even one of these principles or a person whose belief is not compatible with Islam cannot be called a believer in the Quranic sense.
The belief of oneness (Tawheed) is essential in the Quran. It means Allah is One; He is free from needing any partners or helpers in his essence, attributes, and actions. Any belief that contradicts this principle of oneness is shirk (polytheism). Such of belief is not acceptable in the eye of Allah.
As is known, religions are divided into three: heavenly religions, distorted religions, and wrong religions.
“The Religion before Allah is Islam.” (Aal-i Imran, 3:19)
According to the clear decree of the Quranic verse, false religions that are the products of human mind as well as Judaism and Christianity, which lost of their heavenly characteristics by the distortion of the Torah and the Bible, are not valid in the eye of Allah.
“If anyone desires a religion other than Islam, never will it be accepted of him; and in the Hereafter he will be in the ranks of those who have lost.” (Aal-i Imran, 3:85)
When the word religion is used, belief comes to mind first followed by worship. Accordingly, it means belief in God, the understanding of angels, holy books, prophethood, life after death and qadar (predestination) in other belief systems are not compatible with the truth fully.
The rule “If something is definite, it is definite with all of its requirements” is well-known. There are indispensable parts, that is to say, characteristics and conditions for a thing. You cannot think of this particular thing with the absence of those things. For example, when the word spirit is used, life is an indispensable part of it. You cannot think of life without spirit.
Another important creed rule is “Belief does not accept disintegration.” That is to say, one cannot believe some of the principles of belief and disbelieve others. For example, “one who believes in Allah” but “not in the hereafter” is not considered as a believer. It cannot be said that he is a believer in Allah but an unbeliever in the hereafter, by making a dual classification. Similarly, belief in Allah is also a whole.
A person who says, “I believe in Allah but I do not accept that He is pre-eternal” actually believes in a deity he imagines in his mind, not Allah.”
According to these two rules, it is necessary to believe in all of the six principles of belief as the Quran states in order to have a valid belief in Allah. For, it is the perfect book that introduces Allah to humans and jinn; and it is the only heavenly book that has not been distorted.
As is known, the attributes of Allah are divided into two as dhati (personal) attributes and subuti (immutable) attributes.
Personal attributes of Allah are “Wujud (existence)”, “Qidam (eternity)”, “Baqa (everlastingness)”, “Mukhalafatun lil-Hawadith (non-resemblance of the creation)”, “Qiyam bin nafsih (self-existence)”, “Wahdaniyyah (oneness)”. Existing with a necessity being, being eternal and everlasting, not resembling any others, existing because of Himself and not being in need of any beings and being the only One are the attributes that cannot be ascribable to any other deity other than Allah.
Immutable attributes of Allah on the other hand are “Hayah (life)”, “Ilm (knowledge)”, “Iradah (will)”, “Qudrah (power)”, “Sam (hearing)”, “Basar (sight)”, “Kalam (speech)”, “Takwin (creating)”. The only One who has the attributes of life, knowledge, will, power, hearing, sight, speech and creating is Allah. When we say “La Ilaha Illallah”, we express all of these attributes.
When belief in Allah is mentioned, all of these attributes are understood. When even only one is not believed, it cannot be belief in the Quranic sense.
When we have a look at the verses that include the decree; “There is no god but He”, we see that different messages are given prior to and just after this divine decree. Let us view some of them:
“They do blaspheme who say: God is one of three in a trinity: for there is no god but One God (Allah).” (al-Maidah, 5:73)
It means those who believe in trinity deny and move away from the truth.
“Say: O men! I am sent to you all, as the Messenger Allah, to whom belongs the dominion of the heavens and earth: there is no god but He: It is He that gives both life and death.” (al-Araf, 7:158)
Therefore, the belief of a person who believes in a deity who is not the owner of the heavens and earth, who is mortal and in need of help from Allah to resurrect in the Day of Judgment or one that ascribes partners to Allah cannot be considered as true belief in Allah.
“Allah! There is no god but He: of a surety He will gather you together against the Day of Judgment about which there is no doubt.” (an-Nisa, 4:87)
The one who is unable to gather people on the Day of Judgment Day cannot be a deity.
“He it is who shapes you in the wombs as he pleases. There is no god but He, the Exalted in Might, the Wise.” (Aal-i Imran, 3:6)
The one who is unable to shape humans in the womb as Allah wishes cannot be called a deity.
“And call not, besides Allah, on another god. There is no god but He. Everything (that exists) will perish except His own Face. To Him belongs the Command, and to Him will ye (all) be brought back.” (al-Qasas, 28/88)
No being that is bound to perish is a deity.
“Is there a creator other than Allah to give you sustenance from heavens or earth?” (Fatir, 35:3)
Allah, who provides our livelihood by running the Heaven and the Earth together in proper order just like a factory, is one. It is impossible to believe that being who does not have that power is a deity.
“Say: He is my Lord! There is no god but He! On Him is my trust, and to Him do I turn!” (ar-Rad, 13:30)
The belief of those who repent before slaves thinking that they can forgive sins cannot be considered as belief in the Quranic sense.
Another verse about Tawheed:
“He is the First and the Last, the Evident and the Immanent: and He has full knowledge of all things” (al-Hadid, 57:3)
A being that has a beginning and an end, and that is under the control and authority of Allah with everything cannot be called a deity.
There are so many lessons to be taken from these verses by those who believe in trinity. Hz. Isa (Jesus) is a slave. However, he is a slave honored by prophethood. His mother was a righteous woman who was honored to be the mother of a prophet. It is so hard to say that those who go to extremes by attributing deity to them have belief in Allah in the Quranic sense.
It is possible to find important information about Barnabas in "Acts of Apostles", which is accepted by the Church, in the Bible, where the conveyance of the message of the religion by the apostles and what happened to them while doing it are narrated. According to what is narrated there, Barnabas is from Cyprus and his real name is Joseph and he is a Levite. Since Barnabas means “Son of Consolation”, it is probably his nickname.
The name of Barnabas is not mentioned among the apostles in the 'Canonical Bibles'. According to what is understood from ‘Acts of Apostles’, he must have accepted the true religion at an early period. The name of Barnabas is mentioned in the Canonical Bibles as follows for the first time:
“The congregation of believers was one in heart and soul. No one claimed that any of his possessions was his own, but they shared everything they owned. 33With great power, the apostles continued to give their testimony about the resurrection of the Lord Jesus. And abundant grace was upon them all. There were no needy ones among them, because those who owned lands or houses would sell their property, bring the proceeds from the salesand lay them at the apostles’ feet for distribution to anyone as he had need Joseph, a Levite from Cyprus, whom the apostles called BARNABAS sold a field he owned, brought the money, and laid it at the apostles’ feet.” (Acts of Apostles, 4: 32-37).
After this incident, the name of Barnabas is mentioned a lot in Acts of Apostles. Going to town after town, Barnabas declares the word of Allah wherever he goes, does everything to help his brothers and become a means of their acceptance of the true religion.
In the first periods, Barnabas is together with Paul. However, while visiting cities, a sharp disagreement occurs between them whether to take John, who was also called Mark, with them. Then, they left each other. (Acts of Apostles, 15: 36 - 41).
It is interesting that after this separation, the name of Barnabas is not mentioned in Acts of Apostles; Paul is mentioned all the time. We can guess that the disagreement between Barnabas and Paul is a deep one and sharp divisions started after that. As a matter of fact, Barnabas states the following in the introduction of the Gospel:
“Many, being deceived of Satan, under pretence of piety, are preaching most impious doctrine, calling Jesus son of God, repudiating the circumcision ordained of God for ever, and permitting every unclean meat: among whom also Paul hath been deceived, whereof I speak not without grief; for which cause I am writing that truth which I have seen and heard, in the intercourse that I have had with Jesus, in order that ye may be saved, and not be deceived of Satan and perish in the judgment of God.”
According to what we understand from what Barnabas himself wrote, Paul accompanied him for a while as it is mentioned in Acts of Apostles but disagreements occurred among the followers of Hz. Isa (Jesus) after his death as it was the case after the previous prophets; these disagreements went too far and reached the essence of the religion. Paul was among the leaders of those who transformed oneness into polytheism while Barnabas, who adhered to oneness, found it necessary to write down the true religion of Jesus lest those who believe in him should be deceived by Satan.
Is Barnabas really a disciple of Jesus as it is mentioned in the lines above? We cannot answer it as ‘yes’ or ‘no’. However, it is definitely true that Barnabas was a believer in Hz. Isa, who is one of the prophets of Islam, and that he wrote the Gospel during the days or even before the first ‘Canonical Bible’ was written. Barnabas may not have been a disciple of Jesus but he listened to his real disciples; therefore, his Gospel is, with the terminology used in Islamic hadith literature, mursal (a hadith reported by a member of Tabiun who saw and listened to a Companion) if it is not sahih (a hadith reported by a Companion).
Muhammad Ataurrahim, who made a very valuable research on Hz. Isa, accepts that Barnabas was a disciple and gives the following information about his Gospel in brief:
“THE GOSPEL OF BARNABAS is the only known surviving Gospel written by a close disciple of Jesus, that is, by a man who spent most of his lime in the actual company of Jesus, peace be on him, during the three years in which he was delivering his message is the only Bible that was written by a disciple of Jesus, that is, a person who spent most of his time near him during the three-year period he conveyed his message to people and that reached today.”
Barnabas therefore had a direct experience and knowledge of Jesus's teaching, unlike all the authors of the four officially accepted Gospels.
The Gospel of Barnabas was accepted as a canonical Gospel in the churches of Alexandria up until 325 AD. It is also known that it was being circulated in the first and second centuries after the birth of Jesus from the writings of Iraneus (130-200 AD) who wrote in support of the Divine Unity. The famous Council of Nicea was held in 325 AD. The doctrine of Trinity was declared to be the official doctrine of the Pauline Church. The gospels of Matthew, Mark, Luke and John were chosen as the officially accepted gospels of the Church. The remaining Gospels, including the Gospel of Barnabas, were forbidden to read and to have. This prohibition about the Gospel of Barnabas continued in the following years. Pope Damasus (304-384 AD), who became Pope in 366 AD, is recorded as having issued a decree that the Gospel of Barnabas should not be read. This decree was supported by Gelasus, Bishop of Caesaria, who died in 395AD.The Gospel was included in his list of Apocryphal books. 'Apocrypha' simply means 'hidden from the people'. That the Pope included the Gospel of Barnabas in the list of forbidden books shows the existence of this Gospel. In fact, it is known that the Pope secured a copy of the Gospel of Barnabas in 383AD, and kept it in his private library. (Muhammad Ataurrahim, Jesus Prophet of Islam, England 1977, p. 39-41 ).
All of those decrees of prohibition about the Gospel of Barnabas and the precautions that were taken to prevent it from being read could not be successful. The Gospel of Barnabas has existed up to now. The person who enabled the Gospel of Barnabas to reach today wasa monk called Fra Marino:
The manuscript from which the current English translation of the Gospel of Barnabas was made, was originally in the possession of Pope Sixtus V (1589-1590). He had a friend, a monk called Fra Marino, who became very interested in the Gospel of Barnabas after reading the writings of Iraneus, who quoted from it extensively. One day he went to see the Pope. They lunched together and, after the meal, the Pope fell asleep. Father Marino began to browse through the books in the Pope's private library and discovered an Italian manuscript of the Gospel of Barnabas. Concealing it in the sleeve of his robe, he left and came out of the Vatican with it. This manuscript then passed through different hands until it reached a person of great name and authority in Amsterdam, who, during his lifetime, was often heard to put a high value to this piece.' After his death, it came into the possession of J.E.Cramer, a Councillor of the King of Prussia. In 1713, Cramer presented this manuscript to the famous connoisseur of books, Prince Eugene of Savoy. In 1738, along with the library of the Prince, it found its way into the Hofbibliothek in Vienna, where it now rests.Toland, a notable historian of the early Church, had access to this manuscript, and he refers to it in his Miscellaneous Works, which was published posthumously in 1747. He says of the Gospel: "This is in scripture style to a hair." (Ataurrahim, ibid, p. 41-42).
The Italian manuscript was translated into English by Canon Lonsdale and Laura Ragg, and was printed and published by the Oxford University Press in 1907. Nearly the whole edition of this English translation abruptly and mysteriously disappeared from the market. Only two copies of this translation are known to exist, one in the British Museum, and the other in the Library of Congress in Washington. A microfilm copy of the book in the Library of Congress was obtained, and a fresh edition of the English translation was printed in Pakistan. A copy of this edition was used for the purposes of reprinting a revised version of the Gospel of Barnabas thereafter. (Ataurrahim, ibid, p. 42).
The Gospel of Barnabas was translated into Arabic by Dr. Khalil Saada in Egypt; An introduction was written for it and it was published by Muhammad Rashid Riza at the beginning of the twentieth century. (Ahmad Shalabi, Muqaranatu'l-Adyan, Egypt 1984, II, 215)
It is known that the traces of the Gospel of Barnabas have been found in Turkey recently and some studies have been done on it. One of them is Abdurrahman Aygün's "İncil-i Barnaba ve Hz. Peygamber Efendimiz Hakkındaki Tebşîrâtı", which has not been published. It was written in 1942. (see Osman Cilacı, "Barnaba İncili Üzerine Bir Türkçe Yazma ", Diyanet Quarterly, October-November-December,1983, Vol:19, issue: 4, p. 25-35) It is also known that a book in Aramaic written in Syriac alphabet was found in a cave near Hakkari in 1984, that it was the Gospel of Barnabas and that it was captured when it was about to taken out of Turkey. (see İlim ve Sanat, March-April 1986, issue: 6, p. 91-94). In addition, a book was translated into Turkish from English "Barnaba İncili" by Mehmet Yıldız and it was published by Kültür Basın Yayın Birliği in 1988.
The most important points that distinguish the Gospel of Barnabas from the other four Bibles are as follows:
1- The Gospel of Barnabas does not accept the Hz. Isa is a deity or the son of Allah.
2-Hz. Ibrahim's son whom Hz. Ibrahim offered as a sacrifice to Allah is not Ishaq but Ismail, unlike what is stated in the Torah and believed by Christians.
3-The Messiah that is expected to come is not Hz. Isa but Hz. Muhammad.
4-Hz. Isa was not crucified. Yahuda (Judas) Iscariot was resembled to him.
(Muhammad Abu Zahra, Hristiyanlık Üzerine Konferanslar, Trnsl by Âkif Nuri, İstanbul 1978, p. 105-107).
It is clear that the truth cannot be concealed for a long time. Sooner or later, humanity will accept the true religion, maybe in an unprecedented way, and Hz. Ibrahim’s religion of oneness and the prophethood of Hz. Muhammad Mustafa (pbuh), the Seal of the Prophets, will be revived and will dominate the earth in a magnificent way. The wrong is bound to disappear like foam due to its nature and the truth is eternal.
It will be appropriate to mention the content and general theme of the Gospel of Barnabas, the analysis of its text, the criticisms about it and the answers given to them:
The Content of the Gospel of Barnabas
The Gospel of Barnabas consists of an introduction and the main part, in which the life of Jesus is narrated from his birth to his ascension to the sky (222 chapters).
It is stated in the introduction of the Gospel of Barnabas that the book is the real Bible of Jesus, the prophet of Allah, that it was written by his disciple, Barnabas, that many people - Paul is among them - whom Satan deceived spread a wrong creed, that they called Jesus Allah's son, that they did not accept circumcision, which is a pre-eternal vow of Allah, that they decreed that food that is not clean and halal can be eaten and that he wrote this Gospel lest people should be mistaken.
The main part includes the following issues:
1- The birth of Jesus and his childhood (1-9). In this part, Jesus's mother, Maryam (Mary) is given the glad tiding of the birth of Jesus by Gabriel (Jibril) like in the Canonical Bibles (1-2); the birth of Jesus (3-4), his circumcision and offering to the temple (5), the visit of the soothsayers and his flight to Egypt (6-8), his visit to Jerusalem at the age of twelve (9) are narrated.
In this first part of the Gospel of Barnabas, there are big similarities to the Canonical Bibles of Luke and Matthew but there are also some differences. The statement in Luke Bible (1/31-33), "You will conceive and give birth to a son, and you are to call him Jesus. He will be great and will be called the Son of the Most High. The Lord God will give him the throne of his father David, and he will reign over Jacob’s descendants forever; his kingdom will never end" is as follows in the Gospel of Barnabas: "God hath chosen thee to be mother of a prophet, whom he will send to the people of Israel in order that they may walk in his laws with truth of heart." While it is stated in Luke Bible (1/35) that Jesus will be called Son of God because he was born without a father, the same incident is narrated as follows in the Gospel of Barnabas: "O Mary, God who made man without a man is able to generate in thee man with- out a man, because with him nothing is impossible." Instead of the following statement in Luke Bible (2/11), "Today in the town of David a Savior has been born to you; he is the Messiah, the Lord ", the statement in the Gospel of Barnabas is as follows: "For there is born in the city of David a child who is a prophet of the Lord; who bringeth great salvation to the house of Israel."
2- The first year of conveying the message to people (10-46). Jesus having come to the age of thirty years, the angel Gabriel presented to him the Bible at Mount Olives. What God hath done, said and what is written in this book, which descended into the heart of Jesus (10). Thus, the prophethood of Jesus started. This part corresponds to the story of Jesus being baptized in some canonical Bibles. Jesus descends from the mountain and cures a leper (11).
3- The second year of the prophethood of Jesus (47-90). The Roman soldiers in Nain accepting Jesus as God; therefore, Jesus leaving Nain (47), his curing ill people, preaching in the synagogue and retiring into the desert (48-50) his sermons on Satan, last decree and Hell (51-62), his miracles; his instructions related to various issues (63-81), giving the glad tiding of the real Messiah coming after him (82) are narrated.
4- The third year of the prophethood of Jesus (91-222). The following are narrated: Roman soldiers forcing Hebrews to say Jesus is God; Jesus stating that he was not the Messiah and that he was a slave and giving the good news about the real Messiah (96), choosing seventy-two people as disciples (98), the activities of the twelve apostles and seventy-two disciples (99-126), the activities of Jesus in Jerusalem (127-131), Nain (133-138) and Damascus (139-143), his return to Galilee; his statements about the real Pharisees (143-151), his going to Jerusalem from Nazareth (151-162), his instructions about predestination and his statement that only Muhammad had knowledge about this issue; his talks in the desert (163-179), his meeting with Nicodemus, the scribe, in Jerusalem (180-192), the Messiah coming from the descendants of Ismail (Ishmael) (191], the resurrection of Lazarus (193-200), the last incidents in Jerusalem; people looking for Jesus; Gabriel, Michael, Rafael and Uriel taking him and placing him in the third heaven, (215), Judas Iscariot being tortured and crucified (217), Jesus appearing to his mother and his disciples (219-220), Barnabas's questions to Jesus, the answers of Jesus; Jesus addressing Barnabas as, "Barnabas, see that by all means you write my gospel concerning all that has happened through my dwelling in the world"; four angels carrying him up into heaven in the presence of the people there (221), the disciples scattering through the different parts of the world after Jesus; some people - including Paul - claiming that Jesus died and rose again while others claiming that Jesus died and did not rise again; Barnabas reporting the truths (222).
The main theme of the Gospel of Barnabas
The main theme of the Gospel of Barnabas is as follows: God appointed Jesus to teach the truth again since the previous holy scriptures were distorted. The truth that Jesus would teach was the fact that the Messiah would come from the descendants of Ishmael. Jesus is neither God nor the Messiah. He gave the glad tiding that Muhammad would come as the Messiah.
The analysis of the text
The Gospel of Barnabas differs from the canonical Bibles in that it rejects trinity and the deity of Jesus and it states that Jesus is a prophet giving the glad tiding about the real Messiah; therefore, it is regarded as apocryphal by Christians. Christian researchers claim that this Gospel was written in the seventeenth century and that it was written by a Christian who was converted to the religion of Islam; they criticize it in order to prove their claims. Some of the criticisms about the Gospel of Barnabas are reasonable but most of them show that they are biased. The main criticisms are as follows:
1- History and geography mistakes
Acting upon some statements in the Gospel of Barnabas, the critics claim that the writer of this Gospel did not know about the geography of Palestine. Acting upon the statements "Jesus went to the sea of Galilee, and having embarked in a ship sailed to his city of Nazareth" and "Having arrived at the city of Nazareth the seamen..." in the Gospel of Barnabas (Chapter 20), the critics claim that the writer thought that the city of Nazareth was near the sea; acting upon the statements that Jesus went to Nazareth (141), that Jesus then embarked on a ship (151) and Jesus having come to Jerusalem (152) in the same Gospel, they claim that the writer thought both Nazareth and Jerusalem were two cities near the sea. (Benson, p. 14-15).
This information in the Gospel of Barnabas can be interpreted as "The cities of Nazareth and Jerusalem are near the sea and it is possible to travel from one city to the other by ship." However, it can also be interpreted as "The writer did not narrate the places covered in the journey in detail and that he stated the places where an incident started and where it ended." Besides, this interpretation is more compatible with the style of the Gospel of Barnabas. For, it is stated in the same Gospel that Jesus settled in Nazareth, that he went to Jerusalem with his mother Mary when he was twelve years old and that he returned to Nazareth again (9), then he went up to Mount Olives with his mother (10); however, neither the sea nor the ship is mentioned there.
While those statements in the Gospel of Barnabas are claimed to be evidence that this Gospel is fake, the following statement in Matthew Bible is regarded as normal just because it exists in a Bible that is accepted as canonical: "Jesus stepped into a boat, crossed over and came to his own town" (9/1).
It is claimed that a statement in the Gospel of Barnabas (Chapter 99) was mistranslated and that the writer thought the city of Sur (Tyr) was near the river Sharia and it is criticized. However, the writer shows the region where the city of Sur is in another place in the Gospel (21). On the other hand, the phrase "in tiro" in the phrase "in tiro apresso il giordano" in the Italian version shows the city of Sur in Phoenicia. In Italian, this phrase means "directly" or "following". (Cirillo. p. 395)
2- Various concepts that do not comply with the period of Jesus
The critics claim that some information existing in the Gospel of Barnabas indicate the Europe of the Middle Ages notthe period of Jesus and hence it was written in the Middle Age.
A piece of gold that is divided into 60 mites is mentioned in the Gospel of Barnabas (54). This is criticized by saying "There was no currency unit called mite in the period of Jesus; the coin used in the Roman Empire was made of silver, not gold." Mite was used as a currency in the fourteenth century but is it not possible for this word to be used by the translator or the editor of the Gospel of Barnabas? On the other hand, we understand from the New Testament that gold or silver coins were used during the time of Jesus. (Acts of Apostles, 3/6; 20/ 33) Similarly, the criticism of the words barrel used in the Gospel of Barnabas (152) by saying "during the time of Jesus, wine was put in bags made of leather" can be answered by the possibility of that word belonging to the translator. It is claimed that the issues like the way things are done in the court (121), the incident of the duel (99), the existence of sugar (119), and the workers in the quarries (109) show the Europe of the Middle Age not the period of Jesus.
It is not appropriate to criticize acting upon the sentence "Have ye seen them that practise shooting at a mark?" (110) in the Gospel of Barnabas that these kinds of military training are suitable for the Europe of the Middle Age, when there were a lot of soldiers, rather than the period of Jesus. For, it is natural to practice shooting in places where there are soldiers. Mentioning the workers in the quarries (109) does not contradict the facts because the existence of the Solomon's (Sulayman's) Temple and other buildings in Palestine shows the existence of quarries.
Another criticism is the claim that this Gospel, which consists of 222 chapters, was prepared in the form of diatessarons, which were very common in Italy in the thirteenth and fourteenth centuries. The word diatessaron "which means the harmony of four parts" is a name given to the summary of four Bibles in the form of one book; this word was used in this sense for the first time by Tatian for the book he prepared in 150AD. Therefore, diatessaron existed long before the thirteenth and fourteenth centuries.
It is also claimed that in the quotes from the Old Testament used in this Gospel, the Latin translation (Vulgate) by Saint Jerome made in the fourth century AD was used. However, it is also claimed that the Latin translation of the Bible was based on the Gospel of Barnabas. (The Gospel of Barnabas, p. XV)
One of the criticisms is that this Gospel was written by a Christian who was converted to the religion of Islam. However, as Christian critics themselves state, the Gospel of Barnabas contradicts the Quran regarding some issues. While the Quran states that there are seven skies, the Gospel of Barnabas states that there are nine (105, 178). It is stated in the Quran that Hz. Maryam (Mary) had pains when she gave birth to Jesus (Maryam 19/23) but it is stated in the Gospel of Barnabas that she gave birth to him without any pains (3). It is insistently stated in the Gospel of Barnabas that Jesus is not the Messiah (96) but the Quran mentions him as the Messiah (Aal-i Imran 3/45; an-Nisa 4/171-172).
These issues in the Gospel of Barnabas, which contradict the Quran, show that this Gospel could not have been written by Muslims
Conclusion: Trinity and reincarnation(the embodiment of the divine speech and the deity of Jesus) are rejected in the Gospel of Barnabas and the prophethood of Hz. Muhammad (pbuh) is heralded. Advocating the oneness of God, the Gospel of Barnabas (90) states that a child cannot be associated with Him (17), that Jesus is not son of God but only a prophet (1, 2, 4, 10, 11, 15, 19, 31, 44, 47, 52, 71, 82, 83, 96, 112, 156, 157), and that those who call him the son of God will be damned (53, 212). According to this Gospel, the light of Muhammad was created before everything (12, 35, 39, 43), the universe was created for the sake of him, and he will bring mercy and salvation to the whole world (43). When Hz. Adam was created, he saw the name of Muhammad in kalima at-tawhid (39). Hz. Muhammad is the Messenger of Allah (117, 72, 90) and he will explain the words of the previous prophets (17). Jesus is the last prophet before Hz. Muhammad (97). Muhammad will come after Jesus (17, 42) and will eliminate the wrong thoughts about him (97). The messianic promise made by God to Hz. Ibrahim (Abraham) will be realized by Hz. Muhammad (1, 12, 26, 29, 44, 63, 96, 97, 208); and he is the Messiah (39, 41, 42, 44, 54,97, 136, 163,220).
The Gospel of Barnabas, which is regarded as sound by Muslims since it rejects trinity and reincarnation and gives the glad tiding that Hz. Muhammad will come, is rejected by Christians since it contradicts the canonical Bibles and the Christian creed and it is claimed that this Gospel is apocryphal and that it was written in the sixteenth century by a Christian who was converted to the religion of Islam. It is clear that the only existing copy of the Gospel of Barnabas, which is in Italian, is the product of the Italy of that period in terms of the material used to write it, the style and language. However, this does not show that the Gospel attributed to Barnabas was written in that period and that the writer wrote it in Italian and attributed it to Barnabas in order to gain it holiness and authority. Besides, many books in the Old Testament and even the Torah in its current form were not written by the people they are attributed to and they were written afterwards and attributed to those writers; however, they are still accepted as canonical and holy today.
There are evidences that this Gospel was written before the sixteenth century and that a Gospel belonging to Barnabas exists.A decree belonging to the fifth century issued by Gelasus, the Pope, states that the Gospel of Barnabas is apocryphal and mentions it among the forbidden books. In the document called Catalogue des Soixante Livres Canoniques written in Greek in the seventh century, the Gospel of Barnabas is mentioned among the twenty-five apocryphal books. Then, there was a Gospel attributed to Barnabas in the fifth century. The criticism that this Gospel has nothing to do with the Italian copy that exists today is subjective. As for the claim that the Gospel of Barnabas is an apocryphal Gospel that was written in the seventeenth century since it was not mentioned at all from the fifth century to the seventeenth century, it is easy to explain it. Just as the writings by the Jewish-Christian tradition refusing embodiment and trinity were forbidden, so too was the Gospel of Barnabas, which followed the same line, condemned and forbidden by the Church; it was not revealed due to the absolute pressure and authority of the Church.
It does not comply with historical realities to claim that the Gospel of Barnabas was written by a Muslim after the advent of Islam with the effect of Islam because it rejects trinity and does not accept the deity of Jesus. For, some issues in the existing Gospel of Barnabas contradict Islamic beliefs.
In conclusion, the belief that forms the main theme of the Gospel of Barnabas and that adopts the idea that Jesus was not son of God but a prophet, rejecting trinity existed among Christians long before Islam. Accordingly, the Gospel of Barnabas includes the real Gospel, which is described as apocryphal by Paul but the opposite of which is claimed by his followers, the real message given by Jesus. It is a fact that the existing Gospel attributed to Barnabas underwent some additions and interventions along its long historical journey. However, they do not annul the originality and antiquity of its main theme.
For detailed information, see Osman Cilacı, Barnaba İncili item, İslam Ansiklopedisi. TDV Publications