the second. If he is crowded during the first and is unable to prostrate on a back or a foot, he waits until the crowding subsides, then he prostrates and follows his Imam, similar to what was narrated from the Prophet (peace and blessings of Allah be upon him) regarding the Fear Prayer at 'Usfan; a row prostrated with him, while another row remained and did not prostrate with him. When he stood for the second rak'ah, [they prostrated, and that was permitted] (14) due to necessity; it is the same here. Once he completes what is required of him and catches the Imam in standing or bowing, he follows him (15) in it, and the rak'ah is valid for him. The same applies if prostration with his Imam is impossible due to illness, sleep, or forgetfulness, for he is excused in that regard, making him similar to the one who is crowded. If he fears that by preoccupying himself with prostration he will miss the bowing with the Imam in the second rak'ah, he is obligated (16) to follow him, and the second [rak'ah] becomes his first. This is the opinion of Malik. Abu Hanifah said: He should occupy himself with completing the prostration, because he has already bowed with the Imam, so the prostration is incumbent upon him afterward, just as if the crowding had subsided while the Imam was standing. Al-Shafi'i has both views. Our evidence is the saying of the Prophet (peace and blessings of Allah be upon him): "The Imam has been appointed to be followed, so when he bows, then bow" (17). If it is said: He also said: "And when he prostrates, then prostrate," we say: The command to follow in prostration has been waived for this person due to his excuse, while the command to follow in bowing remains applicable because it is possible. Furthermore, because he fears missing the bowing, following his Imam in it becomes mandatory (18) for him (19), like the masbuq (one who joins the prayer late). As for when the Imam is standing, this is not a major disagreement, and the Prophet (peace and blessings of Allah be upon him) did something similar at 'Usfan. Once this is established, if he occupies himself with prostration while believing it is prohibited, his prayer is invalid, because he has intentionally abandoned a mandatory act and performed what is not permissible for him to perform. If he believes it is permissible and prostrates, his prostration is not counted because he