If however, it is done due to forgetfulness, and he does not remember this until after a long time then he should repeat his prayer again. If he remembers a short time later, such as after two or three minutes, then he should complete his prayer and salutation, then prostrate for forgetfulness, and then give salutation (again). The proof of this hadith is Abu Hurayrah (may Allah be pleased with him) who said that, "The Prophet (peace be upon him) lead them in the Dhuhr prayer or the 'Asr prayer and gave the salutation after two raka'at. Then he departed quickly from one of the doors of the mosque, and the people were saying that the prayer had been decreased. The Prophet (peace be upon him) meanwhile, stood by a piece of wood placed in the mosque, leaning against it, as if he was angry. So a man stood and said, 'O Messenger of Allah, have you forgotten or has the prayer been reduced?' So the Prophet of Allah (peace be upon him) said, 'I did not forget nor has it been reduced.' So the man said, 'Rather you have indeed forgotten.' So the Prophet (peace be upon him) said to the Companions, 'Is what he is saying true?' They said 'Yes' So the Prophet (peace be upon him) went forward and prayed what remained of the prayer, then he gave the salutation, then he prostrated twice, then he gave the salutation." [Agreed Upon]