Sahih Muslim 737
Sahih Muslim · Book 6: The Book of Prayer - Travellers · 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
وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ ، حَدَّثَنَا لَيْثٌ ، عَنْ يَزِيدَ بْنِ أَبِي حَبِيبٍ ، عَنْ عِرَاكِ بْنِ مَالِكٍ ، عَنْ عُرْوَةَ ، أَنَّ عَائِشَةَ ، أَخْبَرَتْهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يُصَلِّي ثَلاَثَ عَشْرَةَ رَكْعَةً بِرَكْعَتَىِ الْفَجْرِ .
'A'isha reported that the Messenger of Allah (ﷺ) used to pray thirteen rak'ahs during the night including the two rak'ahs (Sunan) of the dawn prayer.