The ruling on following the imam if he adds a rak'ah in the prayer

The questioner : If people argue that if the imam adds a fifth rak'ah, one should complete it with him and then inform him after the prayer, meaning one says: The Messenger (peace and blessings be upon him) did this and did not disapprove of them for adding it, nor did he point it out to them.

The Shaykh : Yes.

The questioner : And the explanation was delayed.

The Shaykh : We say his argument is correct, but on the condition that he is a prophet to whom revelation is sent. Is that clear or not? Is that possible?

The questioner : Yes, yes, but he says:

The Shaykh : In the time of the Messenger (peace and blessings be upon him), abrogation was possible. That is why they said: Did I add to the prayer? They were in doubt, perhaps it was added by divine law, whereas in reality it had been added. As the man with two hands said: “O Messenger of Allah, did you forget or did you shorten the prayer?” But in our time now, abrogation is not possible.

The questioner : But Shaykh Abu Hasan, if he means that the Messenger (peace and blessings be upon him) means:

The Shaykh : He did not disapprove of them because they were exercising independent legal reasoning. Do you see, if there is a possibility that the prayer was abrogated, is it permissible for them to delay?

The questioner : Yes.

The Shaykh : It is not permissible. As long as there is a possibility that the addition is by divine law, they have no choice but to follow the Messenger (peace and blessings be upon him).

The questioner : Nothing informs them except, for example, Sarah, meaning:

The Shaykh : It is well known that no pointing out is needed for this, because here it is known that the prayer is four rak'ahs and cannot be abrogated.