The main source of thought for Muhammad being illiterate are several verses (7.157-158, 62.2) that describe Muhammad as the "an-nabi al-ummi." In modern Arabic, this means illiteracy but not in Qur'anic Arabic. Palmer translates "illiterate" and Yusuf Ali translates "can neither read nor write" but these are interpritative translations coming from the strong tradition of Muhammad's illiteracy.