The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day
20/27. Chapter:
The command to pray witr
Sunan an-Nasai
أَخْبَرَنَا هَنَّادُ بْنُ السَّرِيِّ، عَنْ أَبِي بَكْرِ بْنِ عَيَّاشٍ، عَنْ أَبِي إِسْحَاقَ، عَنْ عَاصِمٍ، - وَهُوَ ابْنُ ضَمْرَةَ - عَنْ عَلِيٍّ، رَضِيَ اللَّهُ عَنْهُ قَالَ أَوْتَرَ رَسُولُ اللَّهِ صلى الله عليه وسلم ثُمَّ قَالَ " يَا أَهْلَ الْقُرْآنِ أَوْتِرُوا فَإِنَّ اللَّهَ عَزَّ وَجَلَّ وِتْرٌ يُحِبُّ الْوِتْرَ " .
It was narrated that Ali, may Allah (SWT) be pleased with him, said: "The Messenger of Allah (ﷺ) said: "O people of the Qur'an, pray witr, for Allah, the Mighty and Sublime, is Witr (One) and loves Al-Witr (the odd numbered).'"
Reference : Sunan an-Nasa'i 1675In-book reference : Book 20, Hadith 78English translation : Vol. 2, Book 20, Hadith 1676