"And you did not recite before it," meaning: before the Quran, "any book, nor did you write one with your right hand. In that case, the falsifiers would have doubted," meaning: if you had been able to read and write. And the "falsifiers," according to the interpretation of some of them, are: those who did not believe from among the People of the Book.

Muhammad said: The meaning according to this interpretation is: that they find you in their books as an unlettered person, so if you had been able to write, they would have doubted.

Surah al-Ankabut from (verse 49 - verse 52).