“You [O Prophet] could not read any writing [even] before this [revelation], nor could you write at all”
Cited (with Hud 11:49 and Yusuf 12:102) to rebut a narrower objection -- that an unlettered 11-year-old could not have absorbed such detail -- rather than to vouch for the Buhayra account itself, which the lecture treats with real skepticism.