An imam who arrived during the prayer and ordered the congregation to repeat it

Question:
He says: Honorable Shaykh, may Allah grant you success. There is an imam of a mosque who was late for his congregation, so one of them stepped forward and led them in prayer. The imam arrived in the middle of it, so he waited until they finished the prayer, then he stepped forward and said to the congregation, "Since your prayer is invalid, you must repeat it with me." What is your view on what this imam did, and is his statement correct?

Answer:
If the imam who led the prayer behind whom they prayed is one of the nullifiers of Islam, the prayer is not valid. But if he is a Muslim and upright, then what he did is simply a mistake. He said, "I declare it invalid." It was obligatory for him to say, "You were here before I arrived, so do not rush. Do not rush. Pray once. The second time, do not rush." But for him to declare their prayer invalid is a mistake, unless the imam’s prayer is not valid and he knows this about him; that is a different matter. As for saying that a Muslim who did a good deed and led the people in prayer has an invalid prayer, and that the prayer of those behind him is invalid, that is a great error.