What should the congregant do if the imam says the Taslim in the second rak'ah after the middle Tashahhud of a four-rak'ah prayer? Should he say the Taslim with him and alert him, or should he say "Subhanallah" to him without saying the Taslim? And how does the congregant continue his prayer in the event that the imam stands to complete his prayer or does not stand?

If the Imam makes the Taslim erroneously after two rak'ahs of a four-rak'ah prayer, the congregants should alert him by saying "SubhanAllah." If he does not understand, they may speak to him as much as is necessary. If the Imam completes his prayer, they should follow him. If he does not comply, they should complete their prayer individually. Whoever among them intentionally makes the Taslim has invalidated his prayer.