كتاب قيام الليل وتطوع النهار
20
The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day
(35)
Chapter: How to pray witr with one (rak'ah)
(35)
باب كَيْفَ الْوِتْرُ بِوَاحِدَةٍ
It was narrated that Ibn Umar said:
"The Messenger of Allah (ﷺ) said: 'Prayer at night is two by two, and witr is one rak'ah.'"
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا خَالِدُ بْنُ زِيَادٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى وَالْوَتْرُ رَكْعَةٌ وَاحِدَةٌ ‏"‏ ‏.‏
GradeSahih (Darussalam)
Reference : Sunan an-Nasa'i 1693
In-book reference : Book 20, Hadith 96
English translation : Vol. 2, Book 20, Hadith 1694