Masbuq and lahiq: following the imam in his fifth rak‘a

Question

If the imam forgetfully stood up after four rak‘as and someone joined in the fifth rak‘a, how, and how many rak‘as, should that person pray?

Answer

He joined with the intention of the fard. His joining is not valid. He should not join such an imam (Shami, vol. 1, p. 503).

Source: Fatawa Mahmudiyya

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