Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) led us in prayer. He either added something to it or perhaps omitted something. When the Prophet (peace and blessings be upon him) completed the prayer, we said: O Messenger of Allah (peace and blessings be upon him)! Has a new command regarding the prayer been revealed? The narrator says: The Prophet (peace and blessings be upon him) spread out one of his legs and performed two prostrations of forgetfulness (sajda sahw). Then he said: If a new command regarding the prayer had been revealed, I would have informed you about it, but I am also a human being, I forget just as you forget, so when I forget, remind me. And when anyone is uncertain about his prayer, he should try to determine what is correct, base his prayer on that, and then (at the end) perform two prostrations of forgetfulness.

Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) once added something to the prayer while leading us, or perhaps omitted something. It was submitted to him, "O Messenger of Allah (peace be upon him), has a new command regarding the prayer come?" The Prophet (peace be upon him) said: "If a new command had come, I would have informed you about it. But I am also a human being; I forget just as you forget. If any one of you is uncertain about his prayer, then he should consider which option is closer to being correct, and then complete his prayer on that basis, and then perform two prostrations of forgetfulness (sujood as-sahw)." (Imam Ibn Hibban, may Allah have mercy on him, says:) The narrator named Ibrahim bin Mughira is the son-in-law of Abdullah bin Mubarak. And he is trustworthy.

Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates about the Noble Prophet (peace and blessings be upon him): He led five rak'ahs in the Zuhr prayer. It was submitted to him: Has something been added to the prayer? The Noble Prophet (peace and blessings be upon him) inquired: What has happened? They said: You have led five rak'ahs. So the Noble Prophet (peace and blessings be upon him) performed two prostrations of forgetfulness after concluding the prayer with salam.

Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates this statement of the Noble Prophet (peace and blessings of Allah be upon him): "When a person has doubt regarding his prayer, he should try to estimate the correct situation, then say the salam, and then perform two prostrations of forgetfulness (sajda sahw)."

Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) either added something to the prayer or omitted something while leading us in prayer. So it was said: O Messenger of Allah (peace and blessings be upon him)! Has a new command regarding the prayer come? The Prophet (peace and blessings be upon him) said: If a new command had come, I would have informed you about it, but I am a human being; I forget just as you forget. So if any of you has doubt about his prayer, he should consider which situation is closer to being correct and complete his prayer on that basis, then say the salam and perform two prostrations of forgetfulness.

Ibrahim bin Suwaid narrates: Alqamah led us in five rak'ahs in the Zuhr prayer, so Ibrahim said to him: "You have made a mistake." He replied: "O one-eyed! Do you also say this?" Ibrahim answered: "Yes!" So the narrator states: He performed the prostration of forgetfulness (sajda sahw) twice, then Alqamah narrated a similar hadith from the Prophet Muhammad (peace be upon him) on the authority of Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him).

Alqamah narrates: Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) reported this. Once, the Prophet Muhammad (peace and blessings be upon him) led the prayer. The narrator named Ibrahim says: I do not know whether the Prophet (peace and blessings be upon him) added to it or omitted something from it. When he finished the prayer with salam, it was said to him: O Messenger of Allah (peace and blessings be upon him), has a new command regarding the prayer come? The Prophet (peace and blessings be upon him) said: No. What has happened? The people said: You led the prayer in such and such a manner. The narrator says: The Prophet (peace and blessings be upon him) spread his leg, faced the qiblah, performed two prostrations of forgetfulness (sajda sahw), then finished with salam. Then he turned towards us and said: If a new command regarding the prayer had come, I would have informed you about it. But I am also a human being like you; I forget just as you forget. So when I forget, remind me. When a person is in doubt about his prayer, he should try to make the correct estimation. On that basis, he should complete the prayer, then after salam, perform two prostrations of forgetfulness.

Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates this statement of the Noble Prophet (peace and blessings of Allah be upon him): "When a person performs prayer and does not know whether he has performed three rak'ahs or four rak'ahs, then he should perform one more rak'ah and before saying the salam, he should perform the prostration of forgetfulness (sajdah sahw) twice. If he had performed three rak'ahs, then these two prostrations will make them even, and if he had performed four, then these two prostrations will disgrace Satan." (Imam Ibn Hibban, may Allah have mercy on him, says:) This narration has been transmitted by Imam Ahmad ibn Hanbal from Safwan bin Salih.

Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates that the Prophet (peace and blessings of Allah be upon him) said: "When a person has doubt about his prayer, he should put aside the doubt and base his action on what he is certain of. If he is certain that his prayer is complete, then he should perform two prostrations of forgetfulness (sajda sahw). If his prayer was complete, then that rak‘ah will become nafl (supererogatory) and the two prostrations will also be nafl. And if his prayer was incomplete, then that rak‘ah will complete his prayer and these two prostrations will rub the nose of Satan in the dust." (Imam Ibn Hibban, may Allah have mercy on him, says:) "A person who does not have expertise in the science of hadith and does not understand authentic narrations has fallen into the misunderstanding that taharri (making an assumption) and basing action on certainty are the same thing regarding prayer, whereas this is not the case. Taharri is when a person has doubt in his prayer and does not know how much he has prayed. When such a situation arises, it is necessary for him to make an assumption about the correct situation, which is most likely in his view. He should act upon that and after saying salam, perform two prostrations of forgetfulness, as is mentioned in the narration from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him). And the case of basing action on certainty is when a person has doubt between two or three rak‘ahs, or three or four rak‘ahs. So when such a situation arises, he should act upon certainty, which is the lesser number, then complete his prayer and before saying salam, perform two prostrations of forgetfulness, as is mentioned in the narration from Sayyiduna Abdur Rahman bin Awf (may Allah be pleased with him) and Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him). Both methods are Sunnah, and there is no contradiction between the two."

Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates that the Prophet (peace and blessings of Allah be upon him) said: "When a person offers prayer and is unsure whether he has performed three rak'ahs or four, then while he is sitting, he should perform two prostrations of forgetfulness, because Satan comes to a person and says, 'You have become impure (lost your wudu),' so that person should say, 'You are lying.' However, if he hears a sound (of passing wind) with his ears or perceives a smell with his nose, (then the ruling is different)."