When the Imam forgets and stands up to offer a fifth Rak`ah then remembers, should he complete it or sit down?
It is impermissible for a person offering Salah (Prayer) to stand to perform a fifth Rak‘ah in a four-Rak‘ah Salah (Prayer consisting of four units). If they intentionally do this, their Salah will be nullified. But if they mistakenly stand up, they should go back once they remember and they should not complete the fifth Rak‘ah. They should then perform Sujud-ul-Sahw (Prostration of Forgetfulness) and their Salah will be correct.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.