Is a follower required to perform the prostration of forgetfulness if he forgets, adds to, or subtracts from his prayer behind the Imam, such as standing when the Imam sits for the Tashahhud, or sitting when the Imam rises for the next rak'ah?

For the congregant (ma'mum), there are several scenarios regarding the prostration of forgetfulness (sujud al-sahw):

1. If he began the prayer with his imam and a forgetfulness occurred from him (the congregant) but not from his imam, then he does not have to perform the prostration, based on the Prophet's (peace be upon him) saying: "Indeed, the Imam was appointed to be followed, so do not differ from him."

2. If the congregant was a latecomer (masbuq): If he forgot something in what he prayed individually after his imam, he performs the prostration of forgetfulness. If he forgot something in what he prayed with his imam, he also performs the prostration of forgetfulness, according to some scholars.

3. If forgetfulness occurred from the imam and he performed the prostration of forgetfulness, then the congregant is obliged to follow him.

4. If the imam forgot something but did not perform the prostration, even though he believes the prostration is obligatory, then the congregant performs the prostration if he despairs of his imam performing it.