Surah An-Naba 78:20

وَسُيِّرَتِ ٱلْجِبَالُ فَكَانَتْ سَرَابًا

And the mountains are removed and will be [but] a mirage.

Translation: Saheeh International

Tafsir

and the mountains are set in motion dislocated from their positions and become as a mirage as fine dust that is to say like it in terms of its levity when in motion.

Excerpt from Tafsir al-Jalalayn, commentary on 78:20, via Quran.com. The reader has the full commentary and 9 more tafsirs.