(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." (IT)
Reference (IT): Sunan an-Nasa'i 1727 (IT)
In-book reference (IT): Book 20, Hadith 130 (IT)
English translation (IT): Vol. 2, Book 20, Hadith 1728 (IT)