Ruling on following the imam in an extra rak'ah

Question:
This questioner says: If the imam stands up for a fifth rak'ah in the 'Isha' prayer, and when he stands up the worshippers say "Subhan Allah" to him, but he does not sit down, and he completes the rak'ah, and the worshippers behind him stand up, what is the ruling on this rak'ah?
What is the ruling on the action of this imam?

Answer:
It is obligatory to alert him by saying the tasbih. If he does not return, wait until he says the taslim, because he may believe he is correct. So they wait for him until he says the taslim, and they say the taslim with him. The one who does not know that he is mistaken stands up with him. The one who does not know the situation stands up with him, following his imam. The one who knows that the imam is mistaken sits down until he says the taslim with the imam, after the imam has said the taslim.
And whoever believes that he has made a mistake, it is not permissible for him to stand up, but he should be patient. As for the person who has no information whether the imam is correct or not, he follows him, because the default is to follow the imam until he says the taslim with him. Yes.

The presenter: May Allah reward you.