An-Nahl 16:103

وَلَقَدۡ نَعۡلَمُ أَنَّهُمۡ يَقُولُونَ إِنَّمَا يُعَلِّمُهُۥ بَشَرٞۗ لِّسَانُ ٱلَّذِي يُلۡحِدُونَ إِلَيۡهِ أَعۡجَمِيّٞ وَهَٰذَا لِسَانٌ عَرَبِيّٞ مُّبِينٌ 103

And We certainly know that they say, "It is only a human being who teaches the Prophet." The tongue of the one they refer to is foreign, and this Qur'an is [in] a clear Arabic language