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)

Tahdhīb al-Aḥkām|Volume 3|Book 1|Chapter 3

Tahdhīb al-Aḥkām

Volume 3, Book 1, Chapter 3

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)

Commentary #53

وان ذكر كل واحد منهما انه كان مأموما بطلت صلاتهما لان كل واحد منهما قد وكل إلى صاحبه القيام بشرائط الصلاة فلم تصح لهما صلاة

And if two people pray together and each of them remembers that he was intending to be the imam (of prayer), then their prayers are valid. But if each of them remembers that he was intending to follow the other (as a follower), then their prayers are invalid, because each of them entrusted the fulfillment of the conditions of the prayer to the other, so the prayer was not valid for either of them.