The Book of Prayer - Travellers
6/17. Chapter:
Night prayers and the number of rak`ah offered by the Prophet (saws) at night, and that Witr is one rak`ah, and a one-rak`ah prayer is correct
Sahih Muslim
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَزُهَيْرُ بْنُ حَرْبٍ، قَالاَ حَدَّثَنَا وَكِيعٌ، عَنْ سُفْيَانَ، عَنْ أَبِي حَصِينٍ، عَنْ يَحْيَى بْنِ وَثَّابٍ، عَنْ مَسْرُوقٍ، عَنْ عَائِشَةَ، قَالَتْ مِنْ كُلِّ اللَّيْلِ قَدْ أَوْتَرَ رَسُولُ اللَّهِ صلى الله عليه وسلم مِنْ أَوَّلِ اللَّيْلِ وَأَوْسَطِهِ وَآخِرِهِ فَانْتَهَى وِتْرُهُ إِلَى السَّحَرِ .
Masruq reported on the authority of 'A'isha that she said that the Messenger Of Allah (ﷺ) used to observe the Witr prayer every night, maybe in the early part of night, at midnight and in the latter part, finishing his Witr at dawn.
Reference : Sahih Muslim 745bIn-book reference : Book 6, Hadith 166USC-MSA web (English) reference : Book 4, Hadith 1621