Rule about Unlawful Interest
Al-Kāfi|Volume 5|Book 2|Chapter 51
1- عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ عِيسَى عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ هِشَامِ بْنِ سَالِمٍ عَنْ أَبِي عَبْدِ اللهِ (عَلَيْهِ السَّلام) قَالَ دِرْهَمٌ رِبًا أَشَدُّ مِنْ سَبْعِينَ زَنْيَةً كُلُّهَا بِذَاتِ مَحْرَمٍ.
1. A number of our people have narrated from Ahmad ibn Muhammad ibn ‘Isa from Ibn Abi ‘Umayr from Hisham ibn Salim that Abu ‘Abdillah (al-Sadiq) عليه السلام said, “The sin of receiving one dirham of [unlawful] interest is more serious than having seventy carnal relations with one’s mahrams."
- Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (19/122)
- Ṣaḥīḥ al-Kāfī