The ruling on one who adds or subtracts a rak'ah from the prayer

The questioner:
This questioner says: Honorable Shaykh, may Allah preserve you, what is your view regarding a person who prays who subtracts a rak'ah or adds a rak'ah, whether he becomes aware of it immediately after the prayer or after some time has passed?

The Shaykh:
If he adds a rak'ah or subtracts a rak'ah by mistake, then if he subtracts, it is obligatory for him to perform the rak'ah after he has said the taslim. If he realizes he subtracted after the taslim, he should hasten to perform the rak'ah and then prostrate for forgetfulness. However, if a long interval has passed or his wudu' has been broken, it is necessary that he repeat the prayer from the beginning if he left out a rak'ah. If he left out a rak'ah, because he did not complete the prayer. Yes.

The presenter:
May Allah reward you. He says this.

The Shaykh:
If he adds a rak'ah, the prostration for forgetfulness is sufficient. If he remembers it shortly after the taslim, he prostrates for forgetfulness. If a long interval has passed or he forgot it and it was missed, it is dropped.