Masbuqs joining a prayer repeated by an imam who omitted the prostration of forgetfulness

Question

The imam made a mistake in the prayer but did not perform the prostration of forgetfulness (sajda al-sahw). When he began repeating the prayer, the masbuqs broke off their prayer and joined the second congregation. One masbuq completed his prayer and then joined, but did not perform the prostration of forgetfulness, which had been wajib upon the imam; another masbuq performed the prayer together with the prostration of forgetfulness and then joined the second congregation.

Answer

If the imam made such a mistake in the prayer that does not invalidate the prayer but makes the prostration of forgetfulness wajib, and the imam then did not perform the prostration of forgetfulness but repeated [the prayer], then the prayer of those masbuqs who completed their prayer without performing the prostration of forgetfulness and joined the imam is valid; and the…

Source: Fatawa Mahmudiyya

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