The ruling on one who sits for the first tashahhud after the third rak'ah

Question:
A man prayed with the imam and caught the last rak'ah of the 'Asr prayer. After the imam finished the prayer, he stood up to complete his prayer, but he sat for the first tashahhud after the third rak'ah. So, what is the ruling on the prayer?

Answer:
His prayer is valid. However, the tashahhud that he delayed from its obligatory place—he is required to sit after the second rak'ah, after the salam. If he says, "I caught the second rak'ah after the salam," he sits, then stands up and performs the two rak'ahs. This is the place of the tashahhud. So, he moved it from its place and placed it after three rak'ahs, which is the place of the tashahhud. This means he left out the first tashahhud. If he remembers while he is in the prayer, or shortly after the prayer, he prostrates two prostrations for the prostration of forgetfulness. If a long time has passed, his prayer is valid, and the prostration of forgetfulness is not valid for him due to the forgetfulness.