Hadith 1131 — Sahih Muslim | en.tohed.com

#2660 Abu Musa (RA) reported: The day of 'Ashura was one which the Jews respected and they treated it as Id. The Messenger of Allah (ﷺ) said: You also observe fast on this day.... #2661 Abu Musa reported that the people of Khaibar (most of them were Jews) observed fast on the day of 'Ashura and they treated it as 'Id and gave their women ornaments and beautiful dress to wear. The Messenger of Allah (ﷺ) said: You (only) observe fast ...