Sahih al-Bukhari 2005
صحيح البخاري#2005SahihNarrated Abu Musa:The day of 'Ashura' was considered as `Id day by the Jews. So the Prophet (ﷺ) ordered, "I recommend you (Muslims) to 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: 30:110