The Imam Adding to the Prayer After Being Alerted by the Congregation

Question:
His second question: If the imam stands up after completing the prayer but before the closing salam, intending to perform an extra rak'ah beyond the prescribed prayer, and the ma'mum (congregation) point this out to him to alert him to his mistake by saying "Subhan Allah," but he persists in standing for the addition, what is the ruling on this, and what should the ma'mum do after that? Please inform us, may Allah reward you.

Answer:
It is obligatory for the ma'mum to alert the imam; because the Prophet (peace and blessings be upon him) said: . It is obligatory for the imam, if they alert him, to return to his seat, unless he believes that he is correct and they are mistaken. In that case, he acts according to his own belief of correctness and continues until he completes the prayer according to his belief. As for those who alerted him, if they are certain that he is wrong and mistaken, they do not stand with him. They sit, recite the tashahhud, send blessings upon the Prophet (peace and blessings be upon him), and make du'a, and they wait for him until he says the salam, and they say it with him. This is because he is excused, and they are excused. They are excused by their belief that he is mistaken, and he is excused by his belief that he is correct and they are mistaken. So each of them is excused in his ijtihad (independent legal reasoning) and his certainty, in his claim, of his own correctness. When he says the salam, they say it with him.
As for if he does not have certainty, it is obligatory for him to return if the one who alerted him is two or more. He must return if he does not have certainty but only suspicion. He returns just as the Prophet (peace and blessings be upon him) returned due to the statement of Dhu al-Yadayn (the man with two hands) when he alerted him. The Prophet asked the people, and they validated Dhu al-Yadayn, so the Prophet (peace and blessings be upon him) returned and completed his prayer. He did not act according to the statement of Dhu al-Yadayn [in the initial instance] because he was one person. One person does not necessitate returning to his statement unless the imam believes he is correct, in which case he returns. However, if the one alerting is two, he returns to their statement, builds his prayer upon their statement, and leaves his suspicion. This is what is obligatory.
As for the ma'mum, they do not follow him in error, neither in addition nor in omission. If there is an addition, they sit until he says the salam, and they say it with him. If there is an omission and he does not comply, and he sits in the third rak'ah of the Zuhr, for example, or the 'Isha' or the 'Asr, or he sits in the second rak'ah of the Fajr or the Jumu'ah and does not obey them, then they stand to complete their prayer, they complete it and perfect it, and they differ from him; because he erred according to their belief. Yes.
The presenter: May Allah reward you.