What should worshippers do if the imam stands up for an extra (fifth) raka'ah in the Asr prayer, while they are certain that four raka'ahs have been completed, and the imam gestures for them to stand after they have tried to alert him?

If the Imam stands for an extra rak'ah (unit of prayer) by mistake, the congregants must say "Subhan Allah" (Glory be to Allah) and not follow him in the certain excess. If a congregant follows him while knowing, their prayer becomes invalid. If the Imam does not return, the congregants wait for him to conclude the prayer with him. However, if the Imam speaks during the prayer, saying "Stand up," this invalidates his prayer and invalidates the prayer of the congregants if they do not intend to separate from him. Scholars have unanimously agreed on the invalidation of prayer due to intentional speech. The majority of them hold that it invalidates the prayer even if it is for the benefit of the prayer, while some scholars believe that speaking out of ignorance does not invalidate the prayer.