Rule about Unlawful Interest
Al-Kāfi|Volume 5|Book 2|Chapter 51
10- عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ ابْنِ فَضَّالٍ عَنِ ابْنِ بُكَيْرٍ عَنْ عُبَيْدِ بْنِ زُرَارَةَ قَالَ سَمِعْتُ أَبَا عَبْدِ اللهِ (عَلَيْهِ السَّلام) يَقُولُ لا يَكُونُ الرِّبَا إِلا فِيمَا يُكَالُ أَوْ يُوزَنُ.
10. A number of our people have narrated from Ahmad ibn Muhammad from ibn Faddal from ibn Bukayr from ‘Ubayd ibn Zurarah who has said the following: “I once heard abu ‘Abd Allah عليه السلام, saying, ‘Riba’ comes in existence only in what is measured or is weighed.”
- Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (9/126)
- Ṣaḥīḥ al-Kāfī, vol. 2, p. 314