Surah Al-Anbya 21:31

وَجَعَلْنَا فِى ٱلْأَرْضِ رَوَٰسِىَ أَن تَمِيدَ بِهِمْ وَجَعَلْنَا فِيهَا فِجَاجًا سُبُلًا لَّعَلَّهُمْ يَهْتَدُونَ

And We placed within the earth firmly set mountains, lest it should shift with them, and We made therein [mountain] passes [as] roads that they might be guided.

Translation: Saheeh International

Tafsir

And We set in the earth firm mountains lest it should shake with them and We set in them in the firm mountains ravines as roads subulan substitutes for fijājan ‘ravines’ which are wide through-routes that perhaps they may be guided to their destinations during travel.

Excerpt from Tafsir al-Jalalayn, commentary on 21:31, via Quran.com. The reader has the full commentary and 9 more tafsirs.