Surah Al-Qalam 68:2

مَآ أَنتَ بِنِعْمَةِ رَبِّكَ بِمَجْنُونٍ

You are not, [O Muḥammad], by the favor of your Lord, a madman.

Translation: Saheeh International

Tafsir

You are not O Muhammad (s) by the grace of your Lord a madman that is to say madness is precluded in your case on account of your Lord’s grace to you by way of His assigning to you prophethood and in other ways — this was a refutation of their saying that he was a madman.

Excerpt from Tafsir al-Jalalayn, commentary on 68:2, via Quran.com. The reader has the full commentary and 9 more tafsirs.