The ruling if the imam adds an extra rak'ah

Question:
If the imam stands up after the last rak'ah of the prayer out of forgetfulness and straightens his posture, and he is reminded of this, does he return after straightening, or does he pray this extra rak'ah and perform the prostrations of forgetfulness? And when are the two prostrations performed, before the taslim or after the taslim? May Allah reward you with good.

Answer:
It is obligatory for him to return if two people remind him and he did not know that he was correct; in that case, it is obligatory for him to return and perform the prostrations of forgetfulness before he says the taslim. If he delays it until after the salam, there is no harm. The best is for the prostrations of forgetfulness to be before the salam if the forgetfulness is due to doubt about the number of rak'ahs, for he should build upon certainty and prostrate for forgetfulness before the salam. Likewise, if he forgets the first tashahhud or something of the obligatory acts, such as the tasbih in ruku' and sujud, he should prostrate for forgetfulness before the salam; this is the best. If he prostrates after the salam, there is no blame on him. However, if the forgetfulness is due to missing a rak'ah or more, or if he built his prayer upon his predominant opinion, then the prostration for forgetfulness is to be after the salam; this is the best, based on the authentic hadiths reported on this matter. And success is from Allah.