Witr prayer

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ أَخْبَرَنَا مَالِكٌ، عَنْ نَافِعٍ، وَعَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَجُلاً، سَأَلَ رَسُولَ اللَّهِ صلى الله عليه وسلم عَنْ صَلاَةِ اللَّيْلِ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى، فَإِذَا خَشِيَ أَحَدُكُمُ الصُّبْحَ صَلَّى رَكْعَةً وَاحِدَةً، تُوتِرُ لَهُ مَا قَدْ صَلَّى ‏"
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Narrated Ibn Umar: Once a person asked Allah's Messenger (ﷺ) (ﷺ) about the night prayer. Allah's Apostle (ﷺ) replied, "The night prayer is offered as two Rakat followed by two Rakat and so on and if anyone is afraid of the approaching dawn (Fajr prayer) he should pray one Rakah and this will be a Witr for all the Rak`at which he has prayed before."

Sahih Bukhari
(Witr Prayer)
Reference : Sahih al-Bukhari 990
In-book reference : Book 14, Hadith 1