Sahih Muslim 2667
صحيح مسلم#2667SahihAbdullah b 'Abbas reported that the Messenger of Allah (ﷺ) had said:If I live till the next (year), I would definitely observe fast on the 9th, and the narration transmitted by Abu Bakr is:" He meant the day of Ashura
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 13:173