What is the ruling on the prayer of one who led the Maghrib prayer as an imam and performed only one prostration (sujud) in the first unit (rak'ah), then performed the second prostration after being alerted by the congregants, completed the prayer, and performed the two prostrations of forgetfulness (sujud al-sahw) before the taslim? Do the congregants have to repeat their prayer individually? Is it obligatory for the congregant to follow the imam in such a case?

If someone forgets a pillar (rukn) in prayer, then if it is possible to rectify it, they should perform it and whatever comes after it. Otherwise, that rak'ah is invalidated, and they perform a replacement rak'ah and prostrate in forgetfulness (sujud (definition) al-sahw). The definition of 'missing' (fawat) differs among the madhhabs (schools of thought).

The Hanbalis hold that 'missing' occurs upon beginning the recitation of the subsequent rak'ah. In this case, the rak'ah in which the pillar was forgotten is nullified, and the following rak'ah takes its place.

The Malikis hold that 'missing' occurs upon performing the bowing (ruku') of the subsequent rak'ah. If one has not yet performed the bowing, they should perform the forgotten pillar. Otherwise, the deficient rak'ah is nullified, and the performed rak'ah takes its place.

The worshipper must sit to perform the forgotten pillar, such as a prostration (sajdah), because the movement for the pillar is intended.

If the Imam makes a mistake and omits a pillar, the congregants must alert him. If he does not return (to rectify it), they should perform the pillar themselves, then catch up with him and complete the prayer with him. The Imam is not held accountable for forgetfulness because Allah has pardoned this Ummah for mistakes and forgetfulness.