What is the ruling on the prayer of the congregants if the Imam invalidates his ablution during the final Tashahhud: should the Imam say the Taslim or instruct the congregants to complete the prayer?

An Imam who enters prayer and then remembers he is in a state of ritual impurity (حدث) must exit the prayer immediately. If it is a Friday prayer, he must appoint a successor (استخلاف). If it is a prayer other than Friday prayer, it is recommended for him to appoint a successor, but he is permitted to exit without appointing one, and the congregants would complete their prayer individually.