Surah Al-Nahl (The Bees), Verse 103

وَلَقَدْ نَعْلَمُ اَنَّهُمْ یَقُوْلُوْنَ اِنَّمَا یُعَلِّمُهٗ بَشَرٌ لِسَانُ الَّذِیْ یُلْحِدُوْنَ اِلَیْهِ اَعْجَمِیٌّ وَّهٰذَا لِسَانٌ عَرَبِیٌّ مُّبِیْنٌ ۟

Wa laqad na'lamu annahum yaqooloona innamaa yu'allimuhoo bashar; lisaanul lazee yulhidoona ilaihi a'ja miyyunw wa haaza lisaanun 'Arabiyyum mubeen

“We know indeed that they say, "It is a man that teaches him." The tongue of him they wickedly point to is notably foreign, while this is Arabic, pure and clear.”

Quran 16:103 (Yusuf Ali Translation)