Sahih al-Bukhari — Forgetfulness in Prayer — Hadith No: 1229
Translation
Narrated Abu Huraira:The Prophet (ﷺ) offered one of the evening prayers (the sub-narrator Muhammad said, "I think that it was most probably the `Asr prayer") and he finished it after offering two rak`at only. He then stood near a piece of wood in front of the Mosque and put his hand over it. Abu Bakr and `Umar were amongst those who were present, but they dared not talk to him about that (because of excessive respect for him), and those who were in a hurry went out. They said, "Has the prayer been reduced?" A man who was called Dhul-Yadain by the Prophet (ﷺ) said (to the Prophet), "Has the prayer been reduced or have you forgotten?" He said, "Neither have I forgotten, nor has the prayer been reduced." He said, "Certainly you have forgotten." So the Prophet (ﷺ) offered two more rak`at and performed Taslim and then said Takbir and performed a prostration of Sahu like his ordinary prostration or a bit longer and then raised his head and said Takbir and then put his head down and performed a prostration like his ordinary prostration or a bit longer, and then raised his head and said Takbir