Sahih Muslim 573 c
The Book of Mosques and Places of Prayer
As-Sahw (forgetfulness) in prayer and prostrating to compensate for it
Abu Huraira reported: The Messenger of Allah (ﷺ) led us in the 'Asr prayer and gave salutation after two rak'ahs. Dhu'l-Yadain (the possessor of long arms) stood up and said: Messenger of Allah, has the prayer been shortened or have you forgotten? The Messenger of Allah (ﷺ) said: Nothing like this has happened (neither the prayer has been shortened nor have I forgotten). He (Dhu'l-Yadain) said: Messenger of Allah, something has definitely happened. The Messenger of Allah (ﷺ) turned towards people and said: Is Dhu'l-Yadain true (in his assertion)? They said: Messenger of Allah, he is true. Then the Messenger of Allah (ﷺ) completed the rest of the prayer. and then performed two prostrations while he was sitting after salutation.