Surah An-Nahl 16:103

وَلَقَدْ نَعْلَمُ أَنَّهُمْ يَقُولُونَ إِنَّمَا يُعَلِّمُهُۥ بَشَرٌ ۗ لِّسَانُ ٱلَّذِى يُلْحِدُونَ إِلَيْهِ أَعْجَمِىٌّ وَهَـٰذَا لِسَانٌ عَرَبِىٌّ مُّبِينٌ

And We certainly know that they say, "It is only a human being who teaches him [i.e., the Prophet (ﷺ)]." The tongue of the one they refer to is foreign, and this [recitation, i.e., Qur’ān] is [in] a clear Arabic language.

Translation: Saheeh International

Tafsir

And verily wa-laqad is for confirmation We know that they say ‘It is only a human that is teaching him the Qur’ān’ — this was a Christian blacksmith whom the Prophet s used to frequent. …

Excerpt from Tafsir al-Jalalayn, commentary on 16:103, via Quran.com. The reader has the full commentary and 9 more tafsirs.