An-Nahl 16:103

Walaqad naAAlamu annahum yaqooloona innamayuAAallimuhu basharun lisanu allathee yulhidoonailayhi aAAjamiyyun wahatha lisanun AAarabiyyunmubeen

And We certainly know that they say, "It is only a human being who teaches him [i.e., the Prophet (ﷺ)]." The tongue of the one they refer to is foreign, and this [recitation, i.e., Qur’ān] is [in] a clear Arabic language.

We know well that they say, “There is a man who teaches him.” The language of the one they refer to is non-Arabic while this is clear Arabic language.