Islamic Fiqh > Prayer > What invalidates the prayer and the prostration of forgetfulness
What invalidates the prayer, the mistakes that are excused, and the two or three cases of sujud as-sahw.
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Updated on 07 September 2026 at 3:44 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 two 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 two 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 two rak'as, let him take one as the base; if he doubts between two and three, let him take two; if he doubts between three and four, let him take three, and let him perform two prostrations before greeting.al-Bukhari 392, Muslim 572
The rule: always take the lower certain number, then repair with the two 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 two 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 two prostrations. Do not restart the whole prayer for a mere doubt: the Sunna has provided a simple and sufficient repair.
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 two forgetfulness prostrations; a definitively forgotten pillar obliges redoing the rak'a.