Sahih al-Bukhari 4737
صحيح البخاري#4737SahihNarrated Ibn `Abbas:When Allah's Messenger (ﷺ) arrived at Medina, he found the Jews observing the fast on the day of 'Ashura' (10th of Muharram). The Prophet (ﷺ) 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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 65:259