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
← Previous Hadith the Prophet said: "There are no days more beloved to Allah that He be worshipped in them than the ten days of Dhul-Hijjah, fasting every day of them is the equivalent of fasting a year, and standing every night of them (in prayer) is the equivalent of standing on the Night of Qadr."

Jami` at-Tirmidhi Book 8, Hadith 77 Next Hadith → "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