If one remembers during the prayer that he did not perform the second prostration, does he perform it, or does he add a unit of prayer and perform the prostration for forgetfulness before the closing salam?

Question:
What is the ruling if a person is in the first tashahhud and remembers that he did not perform the second prostration? Does he perform it, or does he add a unit of prayer and perform the prostration for forgetfulness before the closing salam? May Allah reward you with good.

Answer:
If he sat for the first tashahhud and remembered that he did not perform the second prostration, then if this prostration was from the first unit of prayer, the first unit is considered invalid. He stands and performs a second unit in its place, then sits for the tashahhud. However, if this prostration was from the second unit of prayer, he goes back and performs the prostration, then sits for the first tashahhud and performs the prostration for forgetfulness afterwards. In all cases, he performs the prostration for forgetfulness. Yes.