Hadith 1391
۞
Allah (swt), the Exalted, said to His Prophet (sw):
"And during the night, pray Tahajjud beyond what is obligatory for you, so that your Lord (azj) may raise you to a praised station" (Surah Al-Isra 17:79).
Thus, the night prayer (Tahajjud) became an obligation upon the Messenger of Allah (sw) due to the command of Allah (swt): 'And during the night, pray Tahajjud.' For others, however, it remains a Sunnah and a supererogatory act.
قال الله تبارك وتعالى لنبيه صلى الله عليه وآله: " ومن الليل فتهجد به نافلة لك عسى أن يبعثك ربك مقاما محمودا " فصارت صلاة الليل فريضة على رسول الله صلى الله عليه وآله لقول الله عز وجل فتهجد، وهي لغيرة سنة ونافلة.