Sahih Muslim 1062
صحيح مسلم#1062SahihAl-Bara' (b. 'Azib), and he was no liar (but a truthful Companion of the Holy Prophet), reported:They used to say prayer behind the Messenger of Allah (ﷺ). I never saw anyone bending his back at the time when he (the Holy Prophet) raised his head, till the Messenger of Allah (ﷺ) placed his forehead on the ground. They then fell in prostration after him
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: 4:224