"One of the wives of the Prophet said: "The Prophet used to fast on the day of 'Ashura, nine days of Dhul-Hijjah and three days each month: The first Monday of the month, and two Thursday."
Sunan an-Nasa'i Book 22, Hadith 283
← Previous Hadith "I heard Mu'awiyah say on the day of 'Ashura when he was on the Mindar: O people of Al-Madinah, where are your scholars? I heard the Messenger of Allah say on this day: "I am fasting, so whoever wants to fast let him do so."

Sunan an-Nasa'i Book 22, Hadith 282 Next Hadith → "The Messenger of Allah said: 'Whoever fasts every day of his life, then he has not fasted."'

Sunan an-Nasa'i Book 22, Hadith 284