Although Abud-Darda became a Muslim the latest in his family, he became a distinguished Companion in a short time thanks to his efforts, self-sacrifice, piety and heroism in jihad.
His real name was "Uwaymir"; "Abud-Darda" was his nickname. The way he became a Muslim is very strange. Although everyone in his family including his wife became Muslims, he could not become a Muslim. Abdullah bin Rawaha, who tried very hard so that he would become a Muslim, was rejected mildly by him each time. Abdullah, however, hoped that one day Abud-Darda would become a Muslim one day and he believed that the cause of Abud-Darda’s delay was due to his researching a lot
One day, Abdullah saw Abu Darda leaving his house. He entered the house from the back door and broke the idol that he always worshipped. Abu Darda’s wife tried to prevent him but Abdullah was determined to break it into pieces. Abu Darda, who came home after a while, saw that all pieces of the idol had been scattered around. He became very angry but he started to think. After a while he said, "If the idol had been something useful, it would have defended itself." He immediately entered into the presence of the Messenger of Allah (pbuh). Hz. Abdullah was there too. He became excited when he saw him. He prayed so that he would attain guidance. He became very happy when he saw that Abu Darda became a Muslim by uttering kalima ash-shahada. 
After entering Islam, Abud-Darda worked for Islam with such enthusiasm and zeal that many people envied him. Abud-Darda did not join the Battle of Badr because he had not yet become a Muslim at that time. However, after Badr, he participated in all of the wars and expeditions. Thanks to his heroism at Uhud, the Messenger of the Prophet (pbuh) complimented him by saying, "Uwaymir is a perfect cavalry man."
After Salman al-Farisi became a Muslim, he became very good friends with Abu Darda at once. The Prophet (pbuh) declared these two self-sacrificing companions, who loved each other very much, as brothers.
Abud-Darda was engaged in trade before becoming a Muslim. After being a Muslim, he gave up trade in order to learn more from the Prophet and to worship more. He started to attend the talks of the Prophet. From time to time, he asked the Messenger of Allah questions. Once, he asked the following question:
"O Messenger of Allah! The rich have earned the world and the hereafter. They perform prayers and fasting; in addition, they give sadaqa. However, we cannot give sadaqa because we are poor."
Thereupon, the Prophet (pbuh) said:
"Shall I tell you something? What you attain when you do it can be attained only by those who do it; those who do not do it cannot attain it by any other way. Say Subhanallah 33 times, Alhamdulillah 33 times and Allahuakbar 34 times after every prayer. "
Hz. Abud-Darda took lessons from everything he saw. He did favors to everybody. He did not hurt anybody. He was good-humored. He smiled especially when he narrated hadiths. When he was asked why, he said, “When the Messenger of Allah said something, he would smile.”
He was generous. He always treated his visitors. He liked to mediate between people. Once, a person whose tooth was broken went to Muawiya and carried on a lawsuit. Muawiya insisted but he did not give up. Abud-Darda was also there. He said, "I heard the Messenger of Allah say, 'If a Muslim is harmed and forgives the person who harms him, Allah Almighty will elevate his rank and forgive one of his mistakes.'" When the man heard this hadith from Abud-Darda, he forgave the man who broke his tooth. 
Abud-Darda was an extraordinarily efficient, modest, knowledgeable man, with an ability of administration; he also did his best to serve Muslims but led a very simple life. Because of these qualities, Hz. Umar wanted to give him an important duty in the state. However, Abud-Darda rejected Hz. Umar’s offer each time.
After a while, Abu'd-Darda asked for permission from Hz. Umar to go to Damascus. Hz. Umar did not allow him by saying, "Unless you accept a duty in the government, I will not let you go to Damascus." However, Abud-Darda’s wish was to go to Damascus and tell the Muslims there about the truths of Islam. He went to Hz. Umar again and said, "Please let me go there and teach people the Sunnah of the Messenger of Allah, lead prayers and tell them the truths that I know!" Then, Hz. Umar allowed him to go to Damascus.
Although Abud-Darda had a deep knowledge in hadith, tafsir and fiqh, he specialized in the Quran. He was one of the rare Companions who memorized the entire Quran when the Prophet was alive. He became very happy when he went to Damascus. He led a plain life and lived in a plain house there. Whenever, he went to the mosque, people would surround him immediately and ask him questions about the Quran, hadith and fiqh; he would answer them with enthusiasm. His knowledge was really great. Muadh bin Jabal, one of the notables of the Companions, said the following when Abud-Darda was about to die:
"O Abud-Darda! The sky has not shadowed anyone more knowledgeable than you, and the earth did not carry anyone more knowledgeable than you."
When the students that Abud-Darda raised became knowledgeable enough, he would immediately form a new circle around them, and he would be busy inspecting all of them. The circles of knowledge (ilm) formed by the students of Abud-Darda after the morning prayer in the Mosque of Damascus had such a lofty view that many people who did not take part in these circles would watch them with pleasure from a corner. Abud-Darda would stand in a corner and answer the questions coming from various circles. There were many distinguished Companions in these circles too. It is reported that Abud-Darda raised approximately 2000 students who knew the Quranic sciences very well in this way.
While Abud-Darda continued his sacred scholarly service, both the governor of Damascus and Yazid Ibn Abi Sufyan led a luxurious life away without heeding the problems of Muslims. Hz Umar heard about it and decided to go to Damascus in order to see the sacred services of Abud-Darda there and to punish the governor. His servant Yarfa was also with him. Hz. Umar sent Yarfa inside in order to try them. After Yarfa entered the mansion of Yazid, Hz. Umar followed him. He ordered all of the velvet cushions, silk goods and other things that were extra to be collected and taken to the Treasury.
The situation of the governor was no different. After doing the same thing to the governor, Hz. Umar said, "Come on! Now let us go to our brother." They went to Abud-Darda 's house. When they entered from the unlocked door that could open when it was pushed, they saw that there was not even a lamp to illuminate the house. Abud-Darda was sitting on a piece of felt in the dark without noticing who the people who entered his house were. Finally, they found each other in darkness and embraced each other.
Abud-Darda could guess the reason for Umar’s unexpected arrival. He said,
"O Umar! You know what the Messenger of Allah said. 'Your share from the world should be as much as the lunch box of a traveler.'"
They chatted until the morning that night.
Hz. Umar put all of the Companions on salary during his caliphate. The salary of those who took part in the Battle of Badr was different. However, Hz. Umar, who was a just caliph, gave Abud-Darda the same salary as them though he had not taken part in the Battle of Badr.
Abud-Darda narrated about 100 hadiths from the Prophet (pbuh). Some of them are as follows:
"On the Day of Resurrection, the heaviest thing in man’s Mizan (Scales) will be high ethics.” 
“Whoever protects his brother's honor, Allah protects his face from Fire on the Day of Resurrection.”
“Whoever was given his share of gentleness, then he has been given a share of good. And whoever has been prevented from his share of gentleness, then he has been prevented from his share of good.”
“Whoever follows a path in the pursuit of knowledge, Allah will make easy for him a path to Paradise. The angels lower their wings in approval of the seeker of knowledge, and everyone in the heavens and on earth prays for forgiveness for the seeker of knowledge, even the fish in the sea. The superiority of the scholar over the worshipper is like the superiority of the moon above all other heavenly bodies. The scholars are the heirs of the Prophets, for the Prophets did not leave behind a Dinar or Dirham, rather they left behind knowledge, so whoever takes it has taken a great share.” 
Abud-Darda died in Damascus in the 32 H. Let us mention some of his nice and significant statements:
“I love three things that are hateful to people: I love poverty, sickness, and death. I love them because poverty is humility, sickness is expiation for sins and death results in a meeting with Allah.”
"Man should not complain about the misfortunes that hit him; he should not tell others about his pains and sorrows; he should not try to acquit himself through his tongue."
"What I am most afraid of is to be asked, "O Uwaymir! Did you learn your religion or not?" on the Day of Resurrection. If I say I learned, I fear that the verses of the Quran that advise what is good and forbid what is evil will witness against me by saying, 'You did not do anything we told you to do and you did not give up the things we told you mot to do."
Hayatus-Sahaba, 1: 231.
Musnad, 5: 196.
ibid, 6: 448.
ibid, 6: 448.
Tirmidhi, Birr: 20; Musnad, 6: 449.
Tirmidhi, Birr: 67.
Ibn Majah, Muqaddima: 17.