Ata bin Yasar said that Abu Saeed Al-Khudri reported the Messenger of Allah صلی اللہ علیہ وسلم as saying: when one of you is in doubt about his prayer (i. e, how much he has prayed), he should throw away his doubt and base his prayer on what he is sure of. When he is sure about the completion of his prayer, he should make two prostrations (at the end of the prayer). If the prayer is complete, the additional rak’ah and the two prostrations will be supererogatory prayer. If the prayer is incomplete, the additional rak’ahs will compensate it, and the two prostrations will be a disgrace for the devil.

Narrated Abdullah ibn Abbas: The Prophet صلی اللہ علیہ وسلم named the two prostrations of forgetfulness disgraceful for the devil.

Narrated Ata ibn Yasar: The Prophet صلی اللہ علیہ وسلم said: When one of you is in doubt about his prayer, and does not know how much he has prayed, three or four rak'ahs, he should pray one (additional) rak'ah and make two prostrations while sitting before giving the salutation. If the (additional) rak'ah which he prayed is the fifth one, he will make it an even number by these two prostrations. If it is the fourth one, the two prostrations will be a disgrace for the devil.

Zaid bin Aslam reported on the authority of the chain of Malik: The Prophet صلی اللہ علیہ وسلم said: If one of you is in doubt about his prayer, and if he is sure that he prayed three rak'ah, he should stand and complete one rak'ah along with its prostrations. Then he should sit and recite the tashahhud. When he finishes the prayer, and there remains nothing except salutation, he should make two prostrations while he is sitting and afterwards should give the salutation. The narrator then narrated the tradition similar to that of Malik. Abu Dawud said: Similarly, this tradition has been narrated by Ibn Wahb from Malik, Hafs bin Maisarah, Dawud bin Qais and Hisham bin Saad. But Hisham projected it to Abu Saeed al-Khudri.