(5) باب مَا جَاءَ فِي الْوِتْرِ بِسَبْعٍ
Umm Salamah narrated:
"The Prophet would perform Witr with thirteen [Rak'ah]. When he was older and became weak he performed Witr with seven." (ES)
Reference (ES): Jami` at-Tirmidhi 457, 458 (ES)
In-book reference (ES): Book 3, Hadith 6 (ES)
English translation (ES): Vol. 1, Book 3, Hadith 457 (ES)