(45) باب الْوِتْرِ بِثَلاَثَ عَشْرَةَ رَكْعَةً
It was narrated that Umm Salamah said:
"The Messenger of Allah (ﷺ) used to pray witr with thirteen rak'ahs, but when he grew older and weaker he prayed witr with nine."
Reference: Sunan an-Nasa'i 1727
In-book reference: Book 20, Hadith 130
English translation: Vol. 2, Book 20, Hadith 1728