Muslims claim that because Muhammad was illiterate, he could not have written the Qur’an, and thus the Qur'an is a miracle, Muhammad's primary miracle. This idea of illiteracy is supported in the Qur’an:
Sura 7:157: "Those who follow the apostle, the unlettered Prophet, whom they find mentioned in their own (scriptures), - in the law and the Gospel...
Sura 7:158 – Say: "O men! I am sent unto you all, as the Apostle of God, to Whom belongeth the dominion of the heavens and the earth: there is no god but He: it is He That giveth both life and death. So believe in God and His Apostle, the Unlettered Prophet, who believeth in God and His words: follow him that (so) ye may be guided."
Thus, the Qur’an’s very existence is testimony to Muhammad’s status as a prophet. There are a couple of problems with this position.
First, it is doubtful that Muhammad was illiterate. Recall that when he was being raised by his uncle, he traveled as a merchant, delivering supplies to various communities. He also traveled extensively with his first wife Khadijah, who hired him to help her with her trade business. Surely there must have been some sort of written record kept to document these transactions. The merchant trade cannot exist without written records of what and how much was shipped to whom.
Second, Muhammad’s illiteracy is irrelevant to the question of the existence of the Qur’an. Muhammad did not write the Qur’an; he recited it. Others wrote down what Muhammad recited, as the Qur’an was complied over several years. The Qur’an would have been written whether Muhammad could or could not read and write, so the argument is irrelevant.
Third, recent scholars have shown that the Arabic word ummi , translated as “illiterate,” does not mean illiterate, but rather means "one who has no book", or those who did not have a book revealed by God (sura 62:2) Thus, the Qur’an was revealed, not to an illiterate prophet, but to a prophet and people who did not have their own book revealed by God.
Sura 62:2 – It is He Who has sent amongst the Unlettered an apostle from among themselves, to rehearse to them His Signs, to sanctify them, and to instruct them in Scripture and Wisdom, - although they had been, before, in manifest error…
Fourth, the hadith includes numerous accounts of Muhammad writing.
Narrated Anas bin Malik:
Once the Prophet wrote a letter or had an idea of writing a letter. The Prophet was told that they (rulers) would not read letters unless they were sealed. So the Prophet got a silver ring made with "Muhammad Allah's Apostle" engraved on it. As if I were just observing its white glitter in the hand of the Prophet… (Sahih al-Bukhari, Volume 1, Book 3, Number 65)
The Prophet wrote the (marriage contract) with 'Aisha while she was six years old and consummated his marriage with her while she was nine years old and she remained with him for nine years (i.e. till his death). (Sahih al-Bukhari, Volume 7, Book 62, Number 88)
Narrated 'Ubaidullah bin 'Abdullah:
Ibn 'Abbas said, "When the ailment of the Prophet became worse, he said, 'Bring for me (writing) paper and I will write for you a statement after which you will not go astray.' But 'Umar said, 'The Prophet is seriously ill, and we have got Allah's Book with us and that is sufficient for us.' But the companions of the Prophet differed about this and there was a hue and cry. On that the Prophet said to them, 'Go away (and leave me alone). It is not right that you should quarrel in front of me." Ibn 'Abbas came out saying, ""It was most unfortunate (a great disaster) that Allah's Apostle was prevented from writing that statement for them because of their disagreement and noise. (Sahih al-Bukhari, Volume 1, Book 3, Number 114)
Thus, the claim that Muhammad was illiterate does not stand up to investigation. Moreover, it is irrelevant. Therefore, the claim that the Qur'an is Muhammad's sole miracle, and divinely inspired since an illiterate man could not have produced it, is also without merit.