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

Muhammad ibn Yahya from Abdillah ibn Muhammad from Ali ibn al-Hakam from Aban ibn Uthman from Abd al-Rahman ibn Abi Abdillah from Abu Abdillah عليه السلام, peace be upon him, who said: Imam al-Sadiq عليه السلام said: “If the imam (of prayer) precedes you by one rak‘ah and you catch the final recitation, then you recite in the third rak‘ah of his prayer, and it is the second for you. But if you only catch one rak‘ah with him, then you recite in that one and in the one that follows it. And if he precedes you by one rak‘ah, you sit in what is the second for you and the third for him, until the rows become upright standing.” He (narrator) said “And Imam عليه السلام said: ‘If you find the imam (of prayer) in prostration, then remain in your place until he raises his head, and if he is sitting, then sit; and if he is standing, then stand.’”