If one intentionally omits the prostration for forgetfulness, is the prayer invalid?

Question : The fifth issue: If one intentionally omits the prostration for forgetfulness, meaning he leaves it out on purpose, is the prayer invalid?

Answer : They say, may Allah have mercy on them, that if one intentionally omits what comes before the closing salam, the prayer is invalid, because he has reduced what is obligatory in the prayer. But if he intentionally omits what comes after the closing salam, it does not invalidate the prayer.
This is because what comes after the closing salam is after the prayer has ended; it is obligatory for the prayer, not obligatory within it. This is unlike the prostration for forgetfulness before the closing salam, which is obligatory within the prayer. Omitting what is obligatory for the prayer does not invalidate the prayer, unlike omitting what is obligatory within it.
Did you understand this rule? Omitting what is obligatory for the prayer does not invalidate the prayer, but omitting what is obligatory within it does invalidate it. For this reason, the prayer is not invalidated by omitting the second call to prayer (iqamah) or by omitting the call to prayer (adhan), because these are obligatory for the prayer. Nor is it invalidated by omitting the congregational prayer, according to the stronger position, because that is obligatory for the prayer, not within it. However, the prayer is invalidated by intentionally omitting the glorifications and the takbir, except for the takbir of the haram, and by omitting all the pillars. Yes.