The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day
20/34. Chapter:
How many (rak'ahs) is witr?
Sunan an-Nasai
أَخْبَرَنَا مُحَمَّدُ بْنُ يَحْيَى بْنِ عَبْدِ اللَّهِ، قَالَ حَدَّثَنَا وَهْبُ بْنُ جَرِيرٍ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي التَّيَّاحِ، عَنْ أَبِي مِجْلَزٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ " الْوَتْرُ رَكْعَةٌ مِنْ آخِرِ اللَّيْلِ " .
It was narrated fom Ibn Umar that: The Prophet (ﷺ) said: "Witr is one rak'ah at the end of the night."
Reference : Sunan an-Nasa'i 1689In-book reference : Book 20, Hadith 92English translation : Vol. 2, Book 20, Hadith 1690