Narrated Ibn Abbas:
When Allah's Apostle arrived at Medina, he found the Jews observing the fast on the day of 'Ashura' (10th of Muharram). The Prophet asked them (about it) and they replied, "This is the day when Moses became victorious over Pharaoh." The Prophet ﷺ said (to the Muslims), "We are nearer to Moses than they, so fast on this day."
Sahih al-Bukhari, Vol. 6, Book of Prophetic Commentary on the Qur'an, Hadith 261
Sahih al-Bukhari, Book of Prophetic Commentary on the Qur'an, Hadith 261