The imam left a prostration and did not perform the prostration for forgetfulness, even though he was reminded by the congregation; what is obligatory for them?

Question:
May Allah reward you, Your Eminence, father. The questioner says: The imam of a mosque led the people in a four-rak'ah prayer. In the second rak'ah, he prostrated only once, then recited the tashahhud and completed his prayer, and did not perform the prostration for forgetfulness, even though he was reminded by the congregation, but he did not notice it. What is required of the congregation in this case?

Answer:
What is the discussion regarding only the prostration for forgetfulness? He missed a complete rak'ah. It was obligatory for him to perform a rak'ah in place of the one from which he left the prostration. He should have completed his prayer and performed the prostration for forgetfulness. However, if he did not perform a rak'ah in place of the one that had only one prostration, he must repeat the prayer. If it was missed and not made up, it must be repeated from the beginning. Yes.