Surah Al-Qari'ah 101:5

وَتَكُونُ ٱلْجِبَالُ كَٱلْعِهْنِ ٱلْمَنفُوشِ

And the mountains will be like wool, fluffed up.

Translation: Saheeh International

Tafsir

and the mountains will be like tufts of wool like carded wool in terms of the lightness with which it floats in the air until it comes to settle upon the earth.

Excerpt from Tafsir al-Jalalayn, commentary on 101:5, via Quran.com. The reader has the full commentary and 9 more tafsirs.