The Funeral Prayer (Salat Al-Janazah)
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 26
وَ رَوَى مُحَمَّدُ بْنُ مُسْلِمٍ عَنْ أَحَدِهِمَا عَلَيْهِمَا اَلسَّلاَمُ قَالَ - سَأَلْتُهُ عَنِ اَلْمَشْيِ مَعَ اَلْجَنَازَةِ فَقَالَ «بَيْنَ يَدَيْهَا وَ عَنْ يَمِينِهَا وَ عَنْ شِمَالِهَا وَ خَلْفِهَا.
Muhammad ibn Muslim narrated from one of them (Imam Muhammad ibn Ali Al-Baqir عليه السلام or Imam Jafar ibn Muhammad Al-Sadiq عليه السلام ) that he asked about walking with the funeral procession. Imam عليه السلام replied: "In front of it, on its right side, on its left side, and behind it."
- Ṣaḥīḥ al-Faqīh, p. 30