Chapter on the Prayer Times (Mawaqit)

Al-Hasan ibn Muhammad from Ibn Ribat from Ibn Miskan from Zurarah, who said: I heard Abu Ja‘far عليه السلام say: "The wall of the mosque of the Messenger of Allah سبحانه وتعالى, may Allah سبحانه وتعالى bless him and his family, was the height of one qamah (the height of a man). When a shadow the length of one arm’s span (dhira‘) had passed, He صلى الله عليه وعلى آله وسلم would pray Dhuhr; when two arm’s spans had passed, He صلى الله عليه وعلى آله وسلم would pray ‘Asr." Then Imam عليه السلام said: "Do you know why one arm’s span and two arm’s spans were set?" I said: "No." Imam عليه السلام said: "Because of the obligatory prayer: when the time of one arm’s span and two arm’s spans arrives, you must begin with the obligatory prayer and leave the supererogatory prayer."