It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, ended the prayer after performing two rak‘ahs. So Dhu’l-Yadayn said: Has the prayer been shortened or did you forget, O Messenger of Allah? The Messenger of Allah, peace and blessings be upon him, said to the people:“Is what Dhu’l-Yadayn says true?”The people said: Yes, he speaks the truth. So the Messenger of Allah, peace and blessings be upon him, stood up and performed two more rak‘ahs, then after giving salam, he said takbir and performed a prostration like his usual prostrations or even greater, then raised his head and said takbir and performed another prostration like his usual prostrations or even greater, then raised his head.

It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, performed the ‘Asr prayer and said the salam after praying two rak‘ahs. Then Dhu’l-Yadayn stood up and said:“Has the prayer been shortened, or did you forget, O Messenger of Allah?”The Messenger of Allah, peace and blessings be upon him, said:“Nothing has happened.”Dhu’l-Yadayn said:“Something has surely happened, O Messenger of Allah!”Then the Messenger of Allah, peace and blessings be upon him, turned to the people and said:“Is Dhu’l-Yadayn telling the truth?”The people said:“Yes.”So the Messenger of Allah, peace and blessings be upon him, stood up and completed whatever was left of the prayer, then performed two prostrations after the salam while he was sitting.

It is narrated from Hazrat Abu Bakr bin Sulaiman that it reached me that the Messenger of Allah (peace be upon him) prayed two rak'ahs of either Zuhr or Asr and then said salam. Then Dhu al-Shimalayn, who was a man from Banu Zuhrah bin Kilab, said, "Has the prayer been shortened, O Messenger of Allah, or did you forget?" The Prophet (peace be upon him) said, "The prayer has not been shortened, nor did I forget." Dhu al-Shimalayn said, "Something did happen, O Messenger of Allah!" So the Prophet (peace be upon him) turned towards the people and said, "Is Dhu al-Yadayn speaking the truth?" The people said, "Yes." So the Messenger of Allah (peace be upon him) completed the remainder of the prayer and then said salam.

This hadith is also narrated in the same way from Sa'id bin al-Musayyib and Abu Salamah bin 'Abd al-Rahman.

Imam Malik, may Allah have mercy on him, said that forgetfulness in prayer is of two types: one is that something is omitted from the prayer due to forgetfulness, in which case the prostration of forgetfulness (sajdah sahw) should be performed before the salam; the other is that something is added to the prayer due to forgetfulness, in which case the prostration of forgetfulness should be performed after the salam.