Islamic Fiqh > Prayer > What invalidates the prayer and the prostration of forgetfulness
What invalidates the prayer, the mistakes that are excused, and the 2 or 3 cases of sujud as-sahw.
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Updated on 06 October 2026 at 10:50 PM
Two distinct situations: invalidating the prayer by a deliberate act, or correcting it after a lapse. The first breaks the prayer, the second is repaired by the 2 prostrations of forgetfulness.
The jurists agree: whoever deliberately adds to his prayer a standing, a sitting, a bowing or a prostration, or removes a pillar from it, invalidates his prayer. The Prophet said: "if one of you forgets, let him perform 2 prostrations" (Muslim 572): the Sunna's ease targets forgetting, not playing with the rite.
Abu Sa'id al-Khudri reports:
If one of you doubts in his prayer and does not know whether he prayed one or 2 rak'as, let him take one as the base; if he doubts between 2 and 3, let him take 2; if he doubts between 3 and 4, let him take 3, and let him perform 2 prostrations before greeting.
al-Bukhari 392, Muslim 572
The rule: always take the lower certain number, then repair with the 2 prostrations.
The scholars agree: the prostration of forgetfulness is valid before the salam as after it.
The Hanafis place it after the salam in every case, relying on the Prophet's word reported by Thawban: "for every lapse 2 prostrations, after greeting" (reported by Abu Dawud). The other schools distribute it: prostration after the salam for a shortfall, before the salam for an addition, according to the details reported from the Companions.
The imam carries the lapse of those praying behind him: the prostration he performs covers the congregation. A hadith of Ibn 'Umar expresses it: "no prostration is due from the one who prays behind the imam; if the imam forgets, it is upon him and upon those behind him" (reported by ad-Darqutni, whose chain was discussed by the hadith scholars).
If you doubt after greeting, lean toward the most probable number and complete with the 2 prostrations. Do not restart the whole prayer for a mere doubt: the Sunna has provided a simple and sufficient repair.
Al-Mughni by Ibn Qudama · Hanbali school
Chapter: the two prostrations of forgetfulness. Imam Ahmad said: five things are preserved from the Prophet (peace and blessings of Allah be upon him): he saluted after two (rak'as) and prostrated, he saluted after three and prostrated, likewise in excess and in deficiency, and he rose after two without pronouncing the tashahhud. And al-Khattabi said: what is authoritative among people of knowledge are these five hadiths, namely the hadiths of Ibn Mas'ud, Abu Sa'id, Abu Hurayra and Ibn Buhayna.
Question 214; Abu al-Qasim said: "Whoever saluted while a part of his prayer remained, performs what remained, salutes, then performs the two prostrations of forgetfulness, then pronounces the tashahhud and salutes, as Abu Hurayra and Imran ibn Husayn reported from the Prophet (peace and blessings of Allah be upon him), who did so."
No: a brief greeting reply is admitted (gesture or short word); any prolonged conversation invalidates.
Excused: the Prophet carried Umama during prayer and set her down when he prostrated (al-Bukhari 516).
If repaired before moving on: nothing; otherwise the 2 forgetfulness prostrations; a definitively forgotten pillar obliges redoing the rak'a.