Surah Al-Fajr 89:2

وَلَيَالٍ عَشْرٍ

And [by] ten nights

Translation: Saheeh International

Tafsir

and by the ten nights the first ten nights of Dhū’l-Hijja

Excerpt from Tafsir al-Jalalayn, commentary on 89:2, via Quran.com. The reader has the full commentary and 9 more tafsirs.