Is the prostration for forgetfulness prescribed for the voluntary prayers?
Machine translationRead the Arabic original
The questioner : The questioner asks: If the imam recites some of the Qur'an to the ma'mum (those praying behind him) while he does not know that the people are not aware of it, does he prostrate?
The Shaykh : The jurists (may Allah have mercy on them) say that this does not necessitate prostration. For every sunnah (recommended practice) in the prayer, prostration is not obligatory for leaving it off or for performing it.
The questioner : And it is not prohibited.
The Shaykh : He says: It is permissible but not prescribed. It is not required of him, nor is he forbidden from it.
The Shaykh : The jurists (may Allah have mercy on them) say that this does not necessitate prostration. For every sunnah (recommended practice) in the prayer, prostration is not obligatory for leaving it off or for performing it.
The questioner : And it is not prohibited.
The Shaykh : He says: It is permissible but not prescribed. It is not required of him, nor is he forbidden from it.
Source
قناة «فضيلة الشيخ محمد بن صالح العثيمين»، 922 - 4600 هل يشرع سجود السهو للسنة؟ ابن عثيمين — youtube.com
The Arabic text is a machine transcription of the audio recording.