Ibn ‘Abbas (R.A), who said: The Prophet (PBUH) came to Madinah and saw the Jews fasting on the day of ‘Ashoora’. He said, “What is this?” They said, “This is a good day, this is the day when Allah saved the Children of Israel from their enemy and Musa fasted on this day.” He said, “We are closer to Musa than you.”So he fasted on this day and told the people to fast. Narrated by Bukhari