Bismillah

Al-jawab billahi at-taufeeq (the answer with Allah's guidance)


Tahajjud salah is a Nafl.

Allah Ta'ala says,

"And spend a portion of the night with the Quraan, as an additional prayer. [17:79]

The Ayah has exhorted us to perform Nafl Salaah at night. Although it is virtuous to perform the Tahajjud Salaah after rising up from ones sleep.

"Abu Hurayrah narrated that he had heard the Messenger of Allah, Muhammad (sallallahu alaihi wa sallam) say that Tahajjud Salah (Late Night Nafl Prayers) is the most important Salah (Prayers) after the Fard Salah (Compulsory Prayers).
(Ahmad)


And Only Allah Ta'ala Knows Best.