Hadith ~ The recommendation to fast Mondays and Thursdays

Hadith- On Good Character

In the Name of Allah, the Most Gracious, the Most Merciful.

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]

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]

Riyad as-Salihin (The Meadows of the Righteous) of Iman Mohieddine Annawawi 631-676.  Chapter 229,  Hadiths  1255 & 1256.