النحل — An-Nahl Ayat 103
وَلَقَدْ نَعْلَمُ اَنَّهُمْ يَقُوْلُوْنَ اِنَّمَا يُعَلِّمُهٗ بَشَرٌۗ لِسَانُ الَّذِيْ يُلْحِدُوْنَ اِلَيْهِ اَعْجَمِيٌّ وَّهٰذَا لِسَانٌ عَرَبِيٌّ مُّبِيْنٌ
Wa laqad na‘lamu annahum yaqūlūna innamā yu‘allimuhū basyar(un), lisānul-lażī yulḥidūna ilaihi a‘jamiyyuw wa hāżā lisānun ‘arabiyyum mubīn(un).
"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."