The Causes of the Prostration for Forgetfulness

Question:
The first message in this episode is from a listener: Muhammad Saleh from Jizan, Abu 'Arish. Our brother has a number of issues, among which is one in which he asks: What are the things that necessitate the prostration for forgetfulness in prayer? I ask for detail on this topic. May Allah reward you with good.

Answer:
In the name of Allah, the Most Gracious, the Most Merciful. Praise be to Allah, and may Allah send prayers and blessings upon the Messenger of Allah, and upon his family and his Companions, and upon those who follow his guidance. As for what follows:
The prostration for forgetfulness has causes; sometimes it is due to an addition in the prayer, and sometimes it is due to a deficiency. The Prophet (peace and blessings be upon him) prostrated for forgetfulness in several matters that occurred to him. He prostrated for forgetfulness when he left the first tashahhud out of forgetfulness and stood up for the third rak'ah; he prostrated two prostrations before the taslim. He prostrated when he said the taslim while short of the full number; he said the taslim after two rak'ahs, then was reminded, completed his prayer, and then prostrated two prostrations for forgetfulness after the taslim. He said the taslim after three rak'ahs, then was reminded, completed his prayer, and prostrated two prostrations for forgetfulness after the taslim. He added a fifth rak'ah in some of his four-rak'ah prayers, and was reminded after the taslim, so he prostrated two prostrations. He said (peace and blessings be upon him): .
So the prostration for forgetfulness is either for a deficiency or for an addition, as you have heard. If one adds a rak'ah, a ruku', or a prostration out of forgetfulness, and he is the imam, the ma'mums remind him of his forgetfulness. He returns to their reminder if he is not certain about what he did. He must perform the prostration for forgetfulness before the taslim, or after it. The better option is before the taslim in all cases of forgetfulness, except if his forgetfulness is due to a deficiency of a rak'ah or more; in that case, it is better for him to prostrate after the taslim.
Likewise, if he acts on his predominant assumption, it is better for him to perform the prostration for forgetfulness after the taslim, based on the hadith of Ibn Mas'ud (may Allah be pleased with him) in which the Prophet (peace and blessings be upon him) said: .
By this, it is known that the prostration for forgetfulness is prescribed for him, and indeed it is obligatory upon him if he does what invalidates his prayer if done intentionally, such as an addition or a deficiency, if he does it out of forgetfulness. If he leaves a prostration from the prostrations, or a ruku', or a rak'ah, or more, he is reminded as mentioned above. He must return to the correct state, complete his prayer, and prostrate for forgetfulness before the taslim in all cases of forgetfulness, except in two situations:
The first is if he says the taslim while short of a rak'ah or more; in that case, he prostrates for forgetfulness after the taslim.
The second situation is if he builds his prayer on his predominant assumption and completes the prayer based on that assumption; in that case, he completes it, says the taslim, and then prostrates two prostrations for forgetfulness after the taslim.
As for if he is uncertain in his prayer and does not have a predominant assumption, he must build on the certainty, and then prostrate two prostrations for forgetfulness before the taslim. This is based on his saying (peace and blessings be upon him) in the hadith of Abu Sa'id: So if he is uncertain whether he prayed two or three, he considers them to be two.
And if he is uncertain whether it is three or four, he considers it to be three and completes it, because of this hadith, the hadith of Abu Sa'id: which Muslim included in his Sahih.
This is what is prescribed, and indeed obligatory, for the believing man and woman when they forget. If one is uncertain in his prayer and does not have a predominant assumption, he must build on the certainty, meaning the lesser number, and complete his prayer based on that, as a precaution for the prayer. If he is uncertain whether he prostrated one or two prostrations, he considers it to be one and performs the second prostration, completing his prayer. If he is uncertain whether he prayed two or three, he considers them to be two and completes his prayer, because this is the certainty and this is the precaution for the prayer. Then, when he finishes the prayer and only the taslim remains, he says the takbir and prostrates two prostrations for forgetfulness, just like his prostration in prayer. His prostration for forgetfulness is the same as his prostration in prayer. He says in it: Subhan Rabbi al-A'la, Subhan Rabbi al-A'la, and he makes du'a in it just as in the prostration of prayer, exactly the same. Then he says the taslim.
As for if he has a predominant assumption, being uncertain whether he prayed two or three, but his predominant assumption is that it is three, he considers it to be three, completes it, says the taslim, and then prostrates two prostrations after the taslim. Except if he is the imam and the ma'mum reminds him; in that case, he gives preference to their reminder and leaves his assumption, returning to their reminder, because their reminder is more reliable than his assumption.
As for if he forgets something that is recommended, not obligatory, the prostration for forgetfulness is not obligatory upon him. For example: if he forgets to raise his hands at the ihram, or at the ruku', or if he forgets and sits cross-legged in the first tashahhud, or if he forgets and sits with his feet to the left in the final tashahhud of a four-rak'ah or three-rak'ah prayer. None of this necessitates the prostration for forgetfulness, because it is not obligatory. And if he prostrates, there is no harm in it for the sake of forgetfulness. Yes.

The presenter : May Allah reward you with good, and may He do you good.