Does the one who joins the prayer late follow the imam if he prostrates for forgetfulness after the closing salam?

The questioner : A man who joined the prayer late: when the imam said the closing salam, he prostrated for forgetfulness. The imam prostrated for forgetfulness, so what does the one who joined late do?

The Shaykh : He must follow him; he prostrates for forgetfulness.

The questioner : Did the imam say the closing salam?

The Shaykh : He does not say the closing salam with him, because if the imam says the closing salam and then prostrates, both options are permissible: it is permissible for the imam to prostrate the prostrations for forgetfulness after the closing salam and before the closing salam. So if the imam says the closing salam, that means he has not contradicted the Shari'ah. As for the one following him, if he knows that the imam made a mistake and that the prostration is required of him, then naturally what I said earlier applies: he must follow. However, out of caution, and especially since the imams of mosques today do not take the dispensation of limiting themselves to a single closing salam, as is established in the Sunnah occasionally—meaning we do not know of an imam who says the closing salam only once—therefore, it is obligatory for the one following to be cautious and not stand up immediately after the imam says his first closing salam, but rather wait for his second closing salam. Here, it will certainly become clear to him whether the imam is going to prostrate the prostrations for forgetfulness or not. In short, if the imam says both closing salams, he stands up, because by doing so he has completed his exit from the prayer. If he says only one closing salam, he does not stand up, in case he intends to prostrate between the two closing salams. This is the detail that should be observed regarding the one who joins late and regarding the imam who is required to prostrate for forgetfulness.