Quran 16:103 from Surah An-Nahl on Divine Marvels.
وَلَقَدۡ نَعۡلَمُ أَنَّهُمۡ يَقُولُونَ إِنَّمَا يُعَلِّمُهُۥ بَشَرٞۗ لِّسَانُ ٱلَّذِي يُلۡحِدُونَ إِلَيۡهِ أَعۡجَمِيّٞ وَهَٰذَا لِسَانٌ عَرَبِيّٞ مُّبِينٌ
English translation: And certainly We know that they say Only teaches him a human being (The) tongue (of) the one they refer to him (is) foreign while this (is) a language Arabic clear
Transliteration: walaqad na'lamu annahum yaquluna innama yu'allimuhu basharun lisanu alladhi yul'hiduna ilayhi a'jamiyyun wahadha lisanun arabiyyun mubinun