يُوتِرُ بِثَلاَثَ عَشْرَةَ رَكْعَةً فَلَمَّا كَبِرَ وَضَعُفَ أَوْتَرَ بِتِسْعٍ .
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."