What is obligatory for the ma'mum (one praying behind the imam) if the imam stands for the fifth rak'ah thinking it is the fourth?
Machine translationRead the Arabic original
Question:
If the imam stands for the fifth rak'ah thinking it is the fourth rak'ah, and he does not pay attention to the ma'mum's alerting him, is it permissible for the ma'mum to leave him?
Answer:
Yes, indeed. Whoever knows that it is an extra rak'ah, it is not permissible for him to follow the imam. Rather, he sits and does not follow him; he intends to pray alone, separate from him. Yes.
If the imam stands for the fifth rak'ah thinking it is the fourth rak'ah, and he does not pay attention to the ma'mum's alerting him, is it permissible for the ma'mum to leave him?
Answer:
Yes, indeed. Whoever knows that it is an extra rak'ah, it is not permissible for him to follow the imam. Rather, he sits and does not follow him; he intends to pray alone, separate from him. Yes.
Source
قناة «العلامة الدكتور صالح الفوزان»، ماذا يجب على المأمومين إذا قام الإمام للركعة الخامسة ظانًّا أنها الركعة الرابعة؟ — youtube.com
The Arabic text is a machine transcription of the audio recording.