Sahih Muslim 871
صحيح مسلم#871SahihAbu Salama reported that Abu Huraira recited takbir in prayer on all occasions of rising and kneeling. We said:O Abu Huraira, what is this takbir? He said: Verily it is the prayer of the Messenger of Allah (ﷺ)
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: 4:34