Sahih Muslim 2686
صحيح مسلم#2686SahihSalama b. Akwa' reported:We, during the lifetime of the Messenger of Allah (ﷺ), in one month of Ramadan (observed fast according to our liking). He who wished to fast lasted and he who wished to break broke it and fed a needy person as an expiation 1544 till this verse was revealed:" He who witnesses among you the month (of Ramadan) he should observe fast during it" (ii)
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: 13:192