What is the ruling on the prayer of one who entered the mosque, and the Friday prayer had already concluded, so he intended to pray Dhuhr, then led someone in prayer aloud, and prayed two rak'ahs?

Whoever misses the Friday prayer should pray Dhuhr as four rak'ahs, and it is not permissible for him to pray Jumu'ah as two rak'ahs. He must repeat it as four rak'ahs and inform the congregants of the obligation to repeat it, because the Prophet, peace and blessings be upon him, said: "Religion is an-naseehah (sincere advice)."