On the recommendation to fast Mondays and Thursdays

Riyad as-Salihin (The Meadows of the Righteous)

by Imam Nawawi

229. Chapter: On the recommendation to fast Mondays and Thursdays

1255. Abu Qatada reported that the Messenger of Allah, may Allah bless him and grant him peace, was asked about fasting Mondays and he said, "That is the day on which I was born and the day when I was sent - or when revelation descended on me." [Muslim]

1256. Abu Hurayra reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "Actions are presented on Mondays and Thursdays, so I like my actions to be presented while I am fasting." (Muslim related it without mentioning fasting.) [at-Tirmidhi]

1257. 'A'isha said, "The Messenger of Allah, may Allah bless him and grant him peace, used to take care to fast on Mondays and Thursdays." [at-Tirmidhi]