English translation
4737. Narrated Ibn ‘Abbās رضي الله عنهما: When Allāh’s Messenger ﷺ arrived at Al-Madīna, he found the Jews observing Ṣaum (fast) on the day of ‘Āshūrā’ (10th of Muḥarram). The Prophet ﷺ asked them (about it) and they replied, “This is the day when Mūsā (Moses) became victorious over Fir’aūn (Pharaoh).” The Prophet ﷺ said (to the Muslims), “We are nearer to Mūsā (Moses) than they, so observe Ṣaum (fast) on this day.”
