On the prostration for forgetfulness; is it before the closing salam or after it?

The questioner : O Shaykh, regarding the prostration for forgetfulness... for the question, if this situation occurs... and the imam finishes, and the prostration... is upon him after the prayer, ... he missed a rak'ah or two, and when the imam says the first closing salam, some of the ma'mum (those praying behind the imam) stand up to complete what is due from them, so what is their status? Do they return... with the imam? Or do they prostrate... for what they missed, or... is it a deviation from the imam?

The Shaykh : ... they follow the imam.

The questioner : But even if he has started...?

The Shaykh : They return from their error.

The questioner : Even if he has started?

The Shaykh: Yes.

The questioner : Okay; what is your opinion regarding the statement of Imam al-Shafi'i that everything reported regarding prostration after the closing salam is based on the knowledge of the Prophet (peace and blessings be upon him) that he forgot to prostrate before the salam, so he prostrated after the prayer...?

The Shaykh : My opinion is the detailed distinction mentioned in some schools of jurisprudence.

The questioner : ... .

The Shaykh : Yes, that there is no difference between the one who added and the one who subtracted; meaning: adding, whether before the salam or without the salam.

The questioner : Adding, whether before or after.

The Shaykh : Yes, yes, that is correct.

The questioner : Even in the case of doubt?

The Shaykh : In everything, yes.
...