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

Ahmad ibn Muhammad from Ali ibn al-Nu‘man from Ibn Muskan from Sulayman ibn Khalid who said: Abu Abdillah عليه السلام, peace be upon him, said: “Regarding a man who catches the imam (of prayer) while he is in rukuh, and if he says the takbir (‘Allahu Akbar’) while his back is still upright, then bows before the imam (of prayer) raises his head, (then) he has caught the rak‘ah”.