Joining the imam in his fifth rak‘a

Question

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

Answer

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

Source: Fatawa Mahmudiyya

Preview. The full text opens with JavaScript enabled.