The ruling on one who prays four rak'ahs in tarawih with a single taslim

Question:
The first message in this episode is a letter sent to the program by the brothers Abdul-Rahman Jum'a Amara, Muhammad Jum'a Amara, and (A. F. G). They ask several questions, the first of which says: Our imam prayed tarawih, and in one of the taslims he stood up for the third rak'ah. He did not remember that he had performed the third rak'ah until he had straightened up standing. At that point, he decided to perform a fourth rak'ah, and he did perform the fourth. Then he recited the tashahhud, prostrated for forgetfulness, and then said the taslim. What is the ruling on what he did?

Answer:
In the name of Allah, the Most Gracious, the Most Merciful.
Praise be to Allah, and may Allah send blessings and peace upon the Messenger of Allah, and upon his family and his Companions, and upon those who follow his guidance. As for what follows:
What is prescribed for one who stands up for the third rak'ah in the tarawih prayer is to go back, sit down, recite the tashahhud, send blessings upon the Prophet (peace and blessings be upon him), and make du'a. Then he should say the taslim after prostrating for forgetfulness twice. If he delays these two prostrations until after the taslim, there is no harm.
It is better for the prostration for forgetfulness to be before the taslim in such a case; because of the saying of the Prophet (peace and blessings be upon him): So he intended two, and it becomes like Fajr: if he stands up for the third, he sits, completes the tashahhud, the sending of blessings upon the Prophet (peace and blessings be upon him), and the du'a, then he prostrates for forgetfulness and says the taslim. But since he did this, he was ignorant, and he completed it as four, and prostrated for forgetfulness, there is no blame on him—Allah willing. Yes.

The presenter: May Allah reward you with good. It was only better that he should suffice with the two, even if he had straightened up standing.

The Shaykh: It is obligatory that he go back; because of the saying of the Prophet (peace and blessings be upon him): So if he stands up for the third while forgetting, it is obligatory for him to go back according to the stronger position, so that he realizes the two he intended. Then he prostrates for forgetfulness and says the taslim after he has recited the tashahhud. And so it is during the day according to the stronger position; because of his saying (peace and blessings be upon him): Meaning: two by two. But if he intended five all together, or seven all together; there is no harm in that; because the Prophet (peace and blessings be upon him) did so. Or if he intended nine all together and sat in the eighth for the first tashahhud, then stood up and performed the ninth, there is no harm.
As for praying four all together, or six all together; no, this is contrary to what is prescribed. It contradicts his saying (peace and blessings be upon him): So nothing is excepted from this except what the Prophet (peace and blessings be upon him) did contrary to that. He (peace and blessings be upon him) performed witr with three all together and did not sit except in the last one. He performed witr with five all together and did not sit except in the last one. He performed witr with seven all together and did not sit except in the last one. And at some times he sat in the sixth, recited the first tashahhud, then stood up for the seventh. And he performed witr with nine all together, and sat in the eighth, recited the first tashahhud, then stood up and performed the ninth. It is not recorded of him (peace and blessings be upon him) that he prayed four all together at night, nor six all together, nor eight all together. Rather, he prays two by two—(peace and blessings be upon him). And he is the one who said—(peace and blessings be upon him): And the Companions saw him praying two by two. And he commanded that, saying: So this is a report whose meaning is a command, its meaning is: pray two by two. May Allah guide them all.

The presenter: O Allah, amen. May Allah reward you with good, and may He do you good.