Everything in this book that is narrated from Abdur Rahman ibn Al-Hajjaj has been transmitted by me from Ahmad ibn Muhammad ibn Yahya Al-Attar - may Allah (swt) be pleased with him - from his father, from Ahmad ibn Muhammad ibn Isa, from Ibn Abi Umayr and Al-Hasan ibn Mahbub together, from Abdur Rahman ibn Al-Hajjaj Al-Bajali Al-Kufi.
He was a freed servant (mawla) who met Imam Al-Sadiq and Imam Musa ibn Jafar (peace be upon them) and narrated from both of them. Imam Musa (as), when Abdur Rahman was mentioned in his presence, would say
"Indeed, he weighs heavily on the heart."