Is it permissible for the one being led in prayer (ma'mum) to return to a forgotten pillar (like bowing) in the first unit of prayer (rak'ah) or in the same unit of prayer in which the忘れ (forgetfulness) was remembered, considering his obligation to follow his imam, and what are the implications of this regarding making up a unit of prayer or performing the prostration of forgetfulness (sujud al-sahw)?

If the worshipper forgets and does not bow with the imam, then remembers it:

- If he remembers it in the second rak'ah, he has missed one rak'ah from the imam's two rak'ahs, and he performs it after the salām.

- If he prostrates with the imam and remembers that he did not bow, he stands up and performs what he missed, then he follows the imam, and he is excused due to his forgetfulness.

- Falling behind the imam due to an excuse (such as sleep or inattentiveness) permits the worshipper to perform what he missed and follow his imam, unless the imam reaches his (the worshipper's) position, in which case he does not perform it, and his rak'ah is valid, made up from the imam's two rak'ahs.

- If he realizes he has fallen behind before the imam reaches his position, he performs what he missed and follows his imam.

- If he falls behind by one rak'ah or more due to an excuse, he follows the imam in the remainder of his prayer and performs what he fell behind on after his imam's salām.

- The Shāfi‘īs hold that if he falls behind the imam by three intended pillars due to an excuse, he follows the imam and performs what he missed after the salām.