(70) باب صَوْمِ النَّبِيِّ صلى الله عليه وسلم - بِأَبِي هُوَ وَأُمِّي - وَذِكْرِ اخْتِلاَفِ النَّاقِلِينَ لِلْخَبَرِ فِي ذَلِكَ
It was narrated that 'Aishah said:
"The Messenger of Allah used to be keen to fast on Mondays and Thursday."
Reference: Sunan an-Nasa'i 2362
In-book reference: Book 22, Hadith 273
English translation: Vol. 3, Book 22, Hadith 2364