16:103
وَلَقَدْ نَعْلَمُ أَنَّهُمْ يَقُولُونَ إِنَّمَا يُعَلِّمُهُۥ بَشَرٌ ۗ لِّسَانُ ٱلَّذِى يُلْحِدُونَ إِلَيْهِ أَعْجَمِىٌّ وَهَـٰذَا لِسَانٌ عَرَبِىٌّ مُّبِينٌ
walaqad naʿlamu annahum yaqūlūna innamā yuʿallimuhu basharun lisānu alladhī yul'ḥidūna ilayhi aʿjamiyyun wahādhā lisānun ʿarabiyyun mubīnun
We know very well that they say, ‘It is a man who teaches him,’ but the language of the person they allude to is foreign, while this revelation is in clear Arabic.
And indeed We know that they (polytheists and pagans) say: "It is only a human being who teaches him (Muhammad صلى الله عليه و سلم)." The tongue of the man they refer to is foreign, while this (the Qur’ân) is a clear Arabic tongue.