Chapter on the Rulings of Congregational Prayer (the Minimum Number for Congregational Prayer, the Description of the Imam, Who Is to Be Followed and Who Is Not to Be Followed, Recitation Behind Both of Them, the Rulings of Those Led in Prayer, and Other Such Rulings Related to It)

This was narrated by Muhammad ibn Yaqub from Ali ibn Ibrahim from his father from al-Nawfali from al-Sakuni from Abu Abdillah عليه السلام, peace be upon him, from his father عليه السلام, peace be upon him, who said: The Commander of the Faithful عليه السلام, peace be upon him, said regarding two men who disagreed (in leading prayer); one of them said, “I was your imam (of prayer),” and the other said, “I was your imam (of prayer).” Imam عليه السلام said: “Their prayers are valid.” I asked: “And if each of them says, ‘I was following you (in prayer)’?” Imam عليه السلام said: “Their prayers are invalid; they must begin (their prayers) again.”