What is the ruling on someone who forgot to bow (rukūʿ), prostrated, then went back, bowed, and completed his prayer?

If the Imam prostrates before bowing, he must return to bowing, then perform what follows. The extra prostration is cancelled, because sequence is a pillar of prayer. Therefore, whoever omits a pillar out of forgetfulness must return to it, unless he has started reciting in the next rak'ah (unit of prayer) or has reached a similar point to the omitted pillar in the next rak'ah. He must perform the prostrations of forgetfulness at the end of his prayer. It is recommended that this be after the salutation because it is for an addition, and it is obligatory according to the Hanbalis and a sunnah according to the majority of scholars.