Standing up for a fifth rak‘a in a four-rak‘a prayer

Question

In a four-rak‘a fard prayer, after four rak‘as, having recited the tashahhud, the imam stood up by mistake. Should he now complete six rak‘as and give the salam, or what should he do? And if he did not recite the tashahhud, what is the ruling? And what should those who joined the imam in the second or third rak‘a do in such a situation?

Answer

If he remembered before performing the prostration of the fifth rak‘a, he should sit down; otherwise he should complete six; and in either case sajda al-sahw will be necessary (lazim). If he did not perform the final sitting and made the prostration of the fifth rak‘a, then the fard prayer has not been validly performed.

Source: Fatawa Mahmudiyya

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