Sahih Muslim 961
صحيح مسلم#961SahihAnas reported:The Messenger of Allah (ﷺ) one day led us in the prayer. and when he completed the Prayer he turned his face towards us and said: 0 People, I am your Imam, so do not precede me in bowing and prostration and in standing and turning (faces, i. e. In pronouncing salutation), for I see you in front of me and behind me, and then said: By Him in Whose hand Is the life of Muhammad, if you could see what I see, you would have laughed little and wept much more. They said: What did you see, Messenger of Allah? He replied: (I saw) Paradise and Hell
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: 4:123