Bismillah!

AsalamuAlaykum Warahmatullahi Wabarakatuh Wa Maghfiratuh,

Allah, the Exalted, says:

"And in some parts of the night (also) perform the Salat (prayer) with it (i.e., recite the Qur'an in the prayer) as an additional prayer (Tahajjud optional prayer - Nawafil) for you (O Muhammad (PBUH)). It may be that your Rubb will raise you to Maqam Mahmud (a station of praise and glory, i.e., the honour of intercession on the Day of Resurrection).'' (17:79)

"Their sides readily forsake their beds, in order to worship their Lord, out of reverence and hope, and from our provisions to them, they give.'' (32:16)

"They used to sleep but little by night [invoking their Rubb (Allah) and praying, with fear and hope].'' (51:17)