If one forgets a rak'ah and then performs it, does he prostrate for forgetfulness before the taslim or after it?

Question:
May Allah reward you, Honorable Shaykh. The questioner says: A person prayed and then said the taslim while forgetting a rak'ah, and then he performed that rak'ah which he had forgotten. Does he prostrate for forgetfulness before the taslim or after it?

Answer:
It is all the same; prostrating before or after is all permissible. However, prostration for forgetfulness due to a deficiency is done before the taslim because it is a compensation. If it is due to an addition, it is done after the taslim because it is to humiliate Satan, not as a compensation.