The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day
20/35. Chapter:
How to pray witr with one (rak'ah)
Sunan an-Nasai
أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ فَضَالَةَ بْنِ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا مُحَمَّدٌ، - يَعْنِي ابْنَ الْمُبَارَكِ - قَالَ حَدَّثَنَا مُعَاوِيَةُ، - وَهُوَ ابْنُ سَلاَّمٍ - عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، قَالَ حَدَّثَنِي أَبُو سَلَمَةَ بْنُ عَبْدِ الرَّحْمَنِ، وَنَافِعٌ، عَنِ ابْنِ عُمَرَ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم أَنَّهُ سَمِعَهُ يَقُولُ " صَلاَةُ اللَّيْلِ رَكْعَتَيْنِ رَكْعَتَيْنِ فَإِذَا خِفْتُمُ الصُّبْحَ فَأَوْتِرُوا بِوَاحِدَةٍ " .
It was narrated from Ibn 'Umar that: He heard the Messenger of Allah (ﷺ) say: "Prayer at night is two rak'ahs by two rak'ahs, then when you fear tat dawn will break, pray witr with one rak'ah."
Reference : Sunan an-Nasa'i 1695In-book reference : Book 20, Hadith 98English translation : Vol. 2, Book 20, Hadith 1696