مَنْ صَلَّى مِنَ اللَّيْلِ فَلْيَجْعَلْ آخِرَ صَلاَتِهِ وَتْرًا فَإِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَأْمُرُ بِذَلِكَ .
It was narrated that Ibn 'Umar said: "Whoever prays during the night, let him make the last of his prayers at night witr, because the Messenger of Allah (ﷺ) used to enjoin that."