Sahih Muslim 4350
صحيح مسلم#4350SahihSulaiman b. Yasar, the freed slave of Maimuna, the wife of Allah's Apostle (ﷺ), narrated from one of the Ansari Companions of Allah's Messenger (ﷺ) that Allah's Messenger (ﷺ) retained (the practice) of Qasama as it was in the pre-Islamic days
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: 28:9