Mas'ar bin Kadam مسعر بن كدام · The Book of Forgetfulness (In Prayer)

"The Messenger of Allah (ﷺ) set out to bring about reconciliation among Banu 'Amr bin 'Awf. The time for prayer came, and the Mu'adhdhin went to Abu Bakr to tell him to gather the people and lead them in prayer. Then the Messenger of Allah (ﷺ) came and passed though the rows until he stood in the first row. The people started clapping to let Abu Bakr know that the Messenger of Allah (ﷺ) had come. Abu Bakr never used…

The Prophet (ﷺ) said: "If one of you does not know whether he prayed three or four (rak'ahs), let him pray a rak'ah then prostrate twice after that when he is sitting. Then if he prayed five (rak'ahs), they (the two prostrations) will make his prayer even-numbered, and if he had prayed four, they will annoy and humiliate the shaitan."

"If one of you is not sure about his prayer, let him estimate what he thinks is most likely to be correct and complete the prayer on that basis, then let him prostrate twice."

The Messenger of Allah (ﷺ) prayed Zuhr then he turned to face them and they said: 'Has there been some change concerning the prayer?' He said: 'Why are you asking?' They told him what he had done, so he turned back toward the Qiblah and prostrated twice. Then he said the salam and turned to face them and said: 'I am only human, I forget as you forget, so if I forget, then remind me.' And he said: 'If there…

That the Messenger of Allah (ﷺ) used to say the taslim to his right and to his left.