Abdullah bin Umm Maktum (r.a.)
Hz. Abdullah, who became a Muslim in the first years of Islam, who was one of the muezzins of Prophet Muhammad, who was one of the first muhajjrs who migrated to Madinah and who was appointed as deputy 13 times by the Prophet during the expeditions and battles in Madinah to lead the prayers, was blind, but his heart and foresight were luminous.
Ibn Umm Maktum's real name was "Amr", but the people of Madinah called him "Abdullah". His father was Qays bin Zaida and his mother was Atika bint Abdullah. He was given the name "Ibn Umm Maktum" meaning "Son of Umm Maktum" in relation to his mother. He was also the son of Hz. Khadijah’s maternal uncle. 
We learn from the talk with the Prophet about when Ibn Umm Maktum lost his eyesight:
According to what Hz. Anas narrates, once Hz. Jibril (Gabriel) entered into the presence of the Prophet. Ibn Umm Maktum was also there. Jibril asked, "When did you lose your eyesight?" He said, “When I was a child.” Thereupon, Jibril gave him the following glad tiding:
"Allah says: 'When I remove the eyesight of a servant, I will give him Paradise as a reward.'"
Thus, Ibn Umm Maktum received the glad tiding of Paradise while he was in the world. 
Hz. Ibn Umm Maktum often went into the presence of the Messenger of Allah after he became a Muslim in order to listen to the Prophet. He memorized the verses of the Quran from the Prophet. Once, the Prophet was conveying the message of Islam to some notables of Quraysh like Utba bin Shayba, Umayya bin Khalaf, and Abu Jahl with the following thought: "Perhaps a few of them will believe and the power of Islam will increase; thus, many people will become Muslims seeing them." Meanwhile, Ibn Umm Maktum arrived and said to the Prophet, "O Messenger of Allah! Read me the Quran. Teach me what Allah taught you."
As the Prophet was busy with the notables of Quraysh, he could not pay attention to Umm Maktum. When Ibn Umm Maktum could not get an answer from the Prophet, he repeated his request a few times. Our Prophet did not heed him and pulled a face; he did not want to be interrupted and continued talking to them. He did not answer Ibn Umm Maktum so that the people there would not laugh sarcastically by saying, "Only weak, poor and blind people and slaves enter this religion." However, after a short time, divine warning was sent down when he finished talking and was about to get up: 
“The (Prophet) frowned and turned away. Because there came to him the blind man (interrupting). But what could tell thee but that perchance he might Grow (in spiritual understanding)? Or that he might receive admonition, and the teaching might profit him? As to one who regards himself as self-sufficient, To him dost thou attend; Though it is no blame to thee if he grow not (in spiritual understanding). But as to him who came to thee striving earnestly, And with fear (in his heart) Of him wast thou unmindful. By no means (should it be so)! For it is indeed a Message of instruction.” 
After this incident, the Prophet complimented Ibn Umm Maktum. Whenever he saw Umm Maktum, he said, "Hello my brother because of whom my Lord warned me!" Sometimes, he laid his cardigan on the ground, made Umm Maktum sit on it and asked him how he was. After that, he treated him like a member of his family. 
Hz. Ibn Umm Maktum was among the first people who migrated to Madinah. He taught people the Quran because he arrived there earlier than others. When the Prophet arrived in Madinah settled there and built the mosque, he gave Umm Maktum the duty of being one of the muezzins, which was regarded as the highest honor.
The Prophet had three muezzins in Madinah: Bilal, Abu Mahzura and Ibn Umm Maktum. When Bilal was not there, Abu Mahzura called adhan; when he was not present, Ibn Umm Maktum called adhan. Ibn Umm Maktum called adhan in Ramadan, telling people that the suhur ended. Therefore, the Prophet said, "Bilal calls adhan at night. Eat and drink until Ibn Umm Maktum calls adhan. "
Hz. Ibn Umm Maktum came to the mosque in all prayers though his house was far away from the mosque and he was blind. Although the Prophet allowed him to perform prayers in his house, he said he would not leave the congregation so as not to miss the duty of calling adhan.
Hz. Umar often guided him when he went to the mosque and when he returned.
Hz. Ibn Umm Maktum was a hafiz of the Quran. He also memorized many hadiths he heard from the Prophet. He was a very pious man.
When jihad started after the Migration, all believers who could fight took part in battles. When verse 95 of the chapter of an-Nisa “Not equal are those Believers who sit (at home) and those who strive” was sent down, the Prophet told Zayd to bring a pencil and paper to write the verse. In the meantime, Hz. Ibn Umm Maktum was also there. He said to the Prophet, "O Messenger of Allah! I would fight if I could but I am blind." Hz. Zayd bin Thabit narrated what happened later as follows:
"Thereupon, Allah sent revelation to the Prophet. In the meantime, the thigh of the Prophet was on my thigh. The weight of the revelation pressed me so much that I was afraid that my knee would be crushed. Then, the traces of the revelation disappeared from the Messenger of Allah. Allah sent down the clause, ‘except those who are disabled (by injury or are blind or lame).’”
It was stated by this verse that jihad was not fard for the ones with excuses and disabilities. Despite this divine permission, Ibn Umm Maktum took part in some wars and frightened the enemy by shouting and yelling. However, the Prophet appointed him as his deputy and as the imam to lead the prayers in Madinah in many battles and expeditions.
Ibn Umm Maktum took part in the Battle of Qadisiyya, which took place during the caliphate of Hz. Umar. He had an armor on his back and a black flag in his hand. He was in a corner and encouraging the mujahids. He scared the enemy with his loud voice. When the war was over, Ibni Umm Maktum was among the martyrs. 
May Allah be pleased with him!
Usdul-Ghaba, 4: 206.
Tabaqat, 4: 206.
ibid, 4: 208.
Abasa, 1: 10.
Tajrid Translation, 2: 580.
Bukhari, Adhan: 10.
Umdatul-Qari, 18: 185.
Isaba, 2: 523.