Sahih Muslim 1714
صحيح مسلم#1714SahihJabir b. Samura reported that the Messenger of Allah (ﷺ) observed (Nafl) prayer sitting before his death
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: 6:144