´It was narrated that Umm Salamah said:` "The Messenger of Allah (ﷺ) used to pray witr with thirteen rak'ahs, and when he grew older and weaker he prayed witr with nine."
Hadith ReferenceSunan an-Nasa'i / The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day / Hadith: 1709
Hadith Gradingالألبانی:صحيح الإسناد | زبیر علی زئی:صحيح