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

From him, from Ahmad ibn Muhammad, from Musa ibn al-Qasim and Abu Qatadah, from Ali ibn Ja’far, from his brother Imam Musa ibn Ja’far عليه السلام, peace be upon them both, who said: I asked Imam al-Khadim عليه السلام about a man who is praying behind the imam (of prayer) and does not know how many units he has prayed, does forgetfulness apply to him? Imam عليه السلام said: “No.”