What is the ruling on the follower if the imam forgets an obligation during prayer and says the Tasleem without performing the prostration of forgetfulness (sujood al-sahw)? Should the follower prostrate for forgetfulness (before or after the Tasleem)? And should he inform the imam of his prostration? What is the imam's duty in this situation: is prostration sufficient, or should he repeat the prayer?

If the Imam makes a mistake and omits an obligatory part of the prayer (such as the first Tashahhud), the congregants should alert him by saying "Subhan Allah" (Tasbih). If he does not rectify the omission, or they do not alert him, and he remembers before the Taslim (salutation), he should perform the prostrations of forgetfulness (sujud al-sahw) before his Taslim. If he does not remember until after he has given the Taslim, and then realizes, he should prostrate after the Taslim, and his prayer will be valid. If he does not prostrate despite knowing about the forgetfulness, his prayer becomes nullified. However, if he does not remember at all, his prayer is valid (according to the Hanbali school). As for the congregant, he should perform the prostration of forgetfulness before the Taslim, even if his Imam omits it, according to the majority of scholars.