Sahih Muslim 6216
صحيح مسلم#6216SahihSa'id b. al-Musayyib reported Abu Musa Ash'ari having said that Allah's Messenger (ﷺ) set out one day to the suburbs of Medina for reliev- ing himself. I followed his steps. The rest of the hadith is the same. Ibn Musayyib said:I concluded (from the manner of their sitting) the (order) of their graves. (The three) would be together (the graves of the Holy Prophet, Hadrat Abu Bakr and Hadrat Umar) and that of 'Uthman would be separate (from them)
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: 44:46