The Chapter on the Virtues of Prayer
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 31
وَقَالَ أَبُو جَعْفَرٍ عَلَيْهِ اَلسَّلاَمُ: «مَا مِنْ عَبْدٍ مِنْ شِيعَتِنَا يَقُومُ إِلَى اَلصَّلاَةِ إِلاَّ اِكْتَنَفَتْهُ بِعَدَدِ مَنْ خَالَفَهُ مَلاَئِكَةٌ يُصَلُّونَ خَلْفَهُ وَ يَدْعُونَ اَللَّهَ عَزَّ وَ جَلَّ لَهُ حَتَّى يَفْرُغَ مِنْ صَلاَتِهِ»
Imam Muhammad ibn Ali Al-Baqir عليه السلام said: "There is no servant from among our followers (Shiite) who stands for prayer except that an equal number of angels, matching those who oppose him, surround him and pray behind him, invoking Allah سبحانه وتعالى, the Mighty and Majestic, for him until he completes his prayer."
- Ṣaḥīḥ al-Faqīh