The ruling on the prayer of the congregation behind an imam who committed an innovation and continued in his prayer

Question:
May Allah reward you, Your Eminence, father. The questioner says: An imam prayed with his congregation, and when he reached the second rak'ah, he remembered that he was not in a state of ritual purity. He completed the prayer because he was hesitant to leave the prayer and have someone from behind him take over. He then repeated the prayer alone. Is his action valid? And what is required of him if his action is not valid?

Answer:
His action is not valid. It is permissible for him to continue in the prayer while not in a state of ritual purity, but if the congregation did not know about this, their prayer is valid. As for him, he made a mistake and it is obligatory for him to repeat the prayer. Yes.