Is a latecomer, whose Imam made a mistake in the part [of the prayer] that he caught up with and prostrated for forgetfulness following him, required to perform another prostration for forgetfulness before his Taslim, or is his prostration with the Imam sufficient?

If the Imam performs the prostration of forgetfulness (sujud al-sahw) before the taslim (salutation), then the latecomer (masbuq) must prostrate with him as an obligation. As for whether the latecomer should repeat the prostration of forgetfulness after completing his prayer, there are two opinions:

1. The first opinion: He should repeat it, because the ruling of forgetfulness became binding upon him, and his prostration with the Imam was for the sake of following. Therefore, what became binding upon him is not waived. This is the more correct view according to the Shafi'is and what Sheikh Ibn Uthaymeen affirmed. 2. The second opinion: He should not repeat it, because the Imam's prostration rectified his prayer and sufficed. This is the opinion of the Malikis, provided that the latecomer caught at least one rak'ah with the Imam.

However, if the Imam's forgetfulness occurred before the latecomer joined the prayer, the latecomer does not need to repeat the prostration.