Dzulhijjah: Allah Swears By The First 10 Days of Dzulhijjah

وَٱلْفَجْرِ ١

By the dawn 

وَلَيَالٍ عَشْرٍۢ ٢

and the ten nights

-> This refers to the first ten days of the month of Dzulhijjah, in which the rituals of pilgrimage are performed. 

وَٱلشَّفْعِ وَٱلْوَتْرِ ٣

and the even and the odd,

- > 10th Dzulhijjah (Eid al-Adha) and 9th Dzulhijjah (the Day of Arafah) 

Surah Al-Fajr verse 1-3

https://quran.com/89