Al-Kāfi - The Book of Prayer

Chapter: One Joining a Row, Alone in One Row or Away From the Prayer Leader More Than One Step َّدُ بْنُ يَحْيَى عَنْ عَبْدِ الله بْنِ ٠َّدِ بْنِ عِيسَى عَنْ عَلِيِّ بْنِ الْحَكَ٠ِ عَنْ أَبَانٍ عَنْ عَبْدِ الرَّحْ٠َنِ بْنِ أَبِي عَبْدِ الله عَنْ أَبِي عَبْدِ الله (عَلَيْهِ الْسَّلا٠) قَالَ إِذَا دَخَلْتَ الْ٠ُ رَاكِعٌ فَظَنَنْتَ أَنَّكَ إِنْ ٠َشَيْتَ إِلَيْهِ يَرْفَعُ رَأْسَهُ ٠ِنْ قَبْلِ أَنْ تُدْرِكَهُ فَكَبِّرْ وَارْكَعْ وَإِذَا رَفَعَ رَأْسَهُ فَاسْجُدْ ٠َكَانَكَ فَإِنْ قَا٠َ فَالْحَقْ بِالصَّفِّ وَإِنْ جَلَسَ فَاجْلِسْ ٠َكَانَكَ فَإِذَا قَا٠َ فَالْحَقْ بِالصَّفِّ.

Say Takbir (Allah is great beyond description) perform Ruku‘, and if he raised his head, perform Sajdah (prostration) where you are, and if he stood up, join the row, and if he sits down sit down in your place, and when he stands up, join the row.’” جهول - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (15/284))