If the imam begins the prayer sitting and the ma'mum (those praying behind him) pray standing, is their prayer invalid?
Machine translationRead the Arabic original
The questioner : If we say that if he begins sitting, it is obligatory for those behind him to sit, and this is the closer view, if they pray standing behind us while we hold that it is obligatory to sit?
The Shaykh : Yes.
The questioner : It does not connect.
The Shaykh : So it is possible to say that their prayer is invalid, because they did something that is prohibited in the prayer itself. And it is possible to say that it is not invalid, because they returned to the original state, and this is a discrepancy in the manner of following the imam.
The questioner : And when the difficulty arises.
The Shaykh : The stronger view is that their prayer is invalid and they must repeat it. Yes.
The Shaykh : Yes.
The questioner : It does not connect.
The Shaykh : So it is possible to say that their prayer is invalid, because they did something that is prohibited in the prayer itself. And it is possible to say that it is not invalid, because they returned to the original state, and this is a discrepancy in the manner of following the imam.
The questioner : And when the difficulty arises.
The Shaykh : The stronger view is that their prayer is invalid and they must repeat it. Yes.
Source
قناة «فضيلة الشيخ محمد بن صالح العثيمين»، 1302 - إذا ابتدأ الإمام الصلاة قعودا وصلى خلفه المأمومون قياما فهل تبطل صلاتهم؟ ابن عثيمين — youtube.com
The Arabic text is a machine transcription of the audio recording.