﴿ وَلَقَدْ نَعْلَمُ أَنَّهُمْ يَقُولُونَ إِنَّمَا يُعَلِّمُهُۥ بَشَرٌۭ ۗ لِّسَانُ ٱلَّذِى يُلْحِدُونَ إِلَيْهِ أَعْجَمِىٌّۭ وَهَٰذَا لِسَانٌ عَرَبِىٌّۭ مُّبِينٌ ﴾

“And, indeed, full well do We know that they say, "It is but a human being that imparts [all] this to him! -[notwithstanding that] the tongue of him to whom they so maliciously point is wholly outlandish, whereas this is Arabic speech, clear [in itself] and clearly showing the truth [of its source].”

(And We know well) O Muhammad (that they) i.e. the disbelievers of Mecca (say: Only a man) Jabr and Yasar (teacheth him) the Qur'an. (The speech of him at whom they falsely hint) incline and ascribe this to (is outlandish) Hebraic, (and this is clear Arabic speech) He says: the Qur'an is in the usage of the Arabic language.