Sahih Muslim 1316
صحيح مسلم#1316SahihIbn 'Abbas said:We used to know that Allah's Messenger (ﷺ) had finished his prayer when we heard the takbir (Allah-O-Akbar)
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: 5:154