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
حَدَّثَنَا ابْنُ نُمَيْرٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا حَنْظَلَةُ، عَنِ الْقَاسِمِ بْنِ مُحَمَّدٍ، قَالَ سَمِعْتُ عَائِشَةَ، تَقُولُ كَانَتْ صَلاَةُ رَسُولِ اللَّهِ صلى الله عليه وسلم مِنَ اللَّيْلِ عَشَرَ رَكَعَاتٍ وَيُوتِرُ بِسَجْدَةٍ وَيَرْكَعُ رَكْعَتَىِ الْفَجْرِ فَتِلْكَ ثَلاَثَ عَشْرَةَ رَكْعَةً .
It is reported on the authority of 'A'isha that the prayer of Allah's Messenger (ﷺ) in the night consisted of ten rak'ahs. He observed a Witr and two rak'ahs (of Sunan) of the dawn prayer, and thus the total comes to thirteen rak'ahs.
Reference : Sahih Muslim 738eIn-book reference : Book 6, Hadith 156USC-MSA web (English) reference : Book 4, Hadith 1611