"The Messenger of Allah took a covenant from me for three: To not sleep except after performing Witr, to fast three days of every month, and to perform the Duha prayer."
Jami` at-Tirmidhi Book 8, Hadith 79
← Previous Hadith the Messenger of Allah said: "Whoever fasts Ramadan, then follows it with six from Shawwal, then that is (equal in reward) to fasting everyday."

Jami` at-Tirmidhi Book 8, Hadith 78 Next Hadith → the Messenger of Allah said: "O Abu Dharr! When you fast three days out of a month, then fast the thirteenth, fourteenth, and fifteenth."

Jami` at-Tirmidhi Book 8, Hadith 80