Surah Taha 20:27

وَٱحْلُلْ عُقْدَةً مِّن لِّسَانِى

And untie the knot from my tongue

Translation: Saheeh International

Tafsir

And undo the knot upon my tongue — the result of his having been burnt by a live coal which he had placed accidentally in his mouth as a child;

Excerpt from Tafsir al-Jalalayn, commentary on 20:27, via Quran.com. The reader has the full commentary and 9 more tafsirs.