(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." (RU)
Reference (RU): Jami` at-Tirmidhi 457, 458 (RU)
In-book reference (RU): Book 3, Hadith 6 (RU)
English translation (RU): Vol. 1, Book 3, Hadith 457 (RU)