Sahih Muslim 282
صحيح مسلم#282SahihIt is narrated on the authority of Abu Musa Ash'ari:He who took up arms against us is not of us
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: 1:188