Anas 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: O 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? (ﷺ) He replied: (I saw) Paradise and Hell.
Abu Hurairah (RA) reported: The Messenger of Allah (ﷺ) said: Does the man who lifts his head ahead of the Imam (from prostration) not fear that Allah may change his head into the head of an ass?
Abu Hurairah (RA) reported: The Messenger of Allah (ﷺ) said: Does the man who lifts his head before the Imam not fear that Allah may change his face into that of an ass?
This hadith has been narrated by Abu Hurairah (RA) by another chain of transmitters except for the words narrated by Rabi' bin Muslim:" Allah may make his face like the face of an ass."