An-Nahl · 16:103

103. I know very well that the idolaters say: It is a human being who is teaching Muhammad (peace be upon him). They are lying in this claim of theirs. The language of the person whom they assume is teaching him is non-Arabic, whereas this Qur’ān has been revealed in the clear and highly eloquent Arabic language. How then do they claim that he received it from a non-Arab?!