Surah Az-Zukhruf 43:52

أَمْ أَنَا۠ خَيْرٌ مِّنْ هَـٰذَا ٱلَّذِى هُوَ مَهِينٌ وَلَا يَكَادُ يُبِينُ

Or am I [not] better than this one [i.e., Moses] who is insignificant and hardly makes himself clear?

Translation: Saheeh International

Tafsir

Or do you perceive in which case am I not better than this one namely Moses who is contemptible feeble and lowly and who can scarcely speak clearly? who can scarcely articulate his speech because of his lisp — which was the result of his accidentally placing a hot coal in his mouth when he was a child.

Excerpt from Tafsir al-Jalalayn, commentary on 43:52, via Quran.com. The reader has the full commentary and 9 more tafsirs.