Chapter on the Virtue of Mosques and Prayer Within Them, and the Virtue of Congregational Prayer and Its Rulings

From him, from Ahmad ibn al-Hasan, from Amr ibn Sa'id, from Musaddiq ibn Sadaqah, from Ammar al-Sabati, from Abu Abdillah عليه السلام, peace be upon him, who said: I asked Imam al-Sadiq عليه السلام about a man who was inattentive behind an imam (of prayer) after he had initiated the prayer, and he did not say anything, nor did he say the takbir, nor the tasbih, nor the tashahhud, until the imam (of prayer) concluded with the salam. Imam عليه السلام said: “His prayer is valid, and if he was inattentive behind the imam (of prayer), there is no obligation upon him to perform the two prostrations of forgetfulness (sajdata al-sahw), because the imam (of prayer) is responsible for the prayer of those behind him.”