If the imam forgets a rak'ah and is reminded after he has said the taslim, does he say the takbir of ihram, or does he stand up to complete it without takbir, and when does he perform the prostration for forgetfulness?

Question:
He says: If the imam doubts in the four-rak'ah prayer and does not know whether he prayed three or four, then he says the taslim, and after the taslim some of the ma'mum inform him that he only prayed three. In this case, does the imam say the takbir of ihram for the fourth rak'ah, or does he simply stand up and recite al-Fatihah without takbir? And what is the position of the prostration for forgetfulness, before the taslim or after it?

Answer:
If he says the taslim before completing the prayer and then remembers, or is reminded, that it was incomplete, he returns and faces the qiblah. The imam faces the qiblah, then stands up without takbir. The takbir he said when rising from the prostration is sufficient. He stands without takbir and recites al-Fatihah and whatever is easy for him after it, or he does not recite anything after it, because this is the last rak'ah. He does not recite anything after al-Fatihah. Then he sits and recites the final tashahhud. Then he does what is best: if he wishes, he prostrates before the taslim, the two prostrations of forgetfulness; and if he wishes, he prostrates after the taslim. This is better. Prostrating after the taslim is better in this case, because it is a prostration for an addition to the prayer, which is the taslim before its completion.