“If he realizes this after the final salām, it is as though he had omitted an entire rak'ah.”

His statement, “If he realizes this after the final salām, it is as though he had omitted an entire rak'ah,” means that if he realizes, after ending the prayer with the final salām, that he omitted a pillar, it is treated as though he had ended the prayer with an entire rak'ah missing. Accordingly, he must perform a complete rak'ah, then recite the tashahhud (testimony of faith), perform the prostration of forgetfulness, and end with the salām—either after it or before it, as we shall mention, Allah willing.

An example is a man who prays and, after finishing the prayer, remembers that he performed only one prostration in the final rak'ah. He must perform a complete rak'ah. This is what the author has determined.

The reasoning is that, once he has ended the prayer with the final salām, it is no longer possible to build one part of the prayer upon another; thus, the entire rak'ah is invalidated, and he must perform a complete rak'ah. Moreover, his ending the prayer with the salām after the tashahhud resembles his beginning the recitation of the rak'ah that follows it. If he begins reciting the following rak'ah, he must disregard the preceding rak'ah and perform a complete rak'ah.

The second view (1) is that he is not required to perform a complete rak'ah; rather, he need only perform what he omitted and what comes after it. This is because what preceded the omitted act was performed validly in its proper place, so a person is not required to repeat it. As for what follows the omitted act, it is only required to be repeated in order to preserve the proper sequence. Thus, in the example mentioned, we would say to this man: Return, sit between the two prostrations, perform the second prostration, then recite the tashahhud, then end with the salām; then perform the prostration of forgetfulness and end with the salām. This view is the correct one.