Ibn `Abbas:
When the Prophet (ﷺ) arrived at Medina he found that the Jews observed fast on the day of 'Ashura'. They
were asked the reason for the fast. They replied, "This is the day when Allah caused Moses and the
children of Israel to have victory over Pharaoh, so we fast on this day as a sign of glorifying it."
Allah's Messenger (ﷺ) said, "We are closer to Moses than you." Then he ordered that fasting on this day
should be observed.