Chapter on Currency Exchange and Its Forms
Man Lā Yaḥḍuruh al-Faqīh|Volume 3|Book 2|Chapter 29
وَ رَوَى صَفْوَانُ عَنْ إِسْحَاقَ بْنِ عَمَّارٍ قَالَ: سَأَلْتُ أَبَا إِبْرَاهِيمَ عَلَيْهِ اَلسَّلاَمُ عَنِ اَلرَّجُلِ يَكُونُ لِي عَلَيْهِ اَلْمَالُ فَيَقْضِينِي بَعْضاً دَنَانِيرَ وَ بَعْضاً دَرَاهِمَ فَإِذَا جَاءَ يُحَاسِبُنِي لِيُوَفِّيَنِي جَاءَ وَ قَدْ تَغَيَّرَ سِعْرُ اَلدَّنَانِيرِ أَيَّ اَلسِّعْرَيْنِ أَحْسُبُ اَلَّذِي كَانَ يَوْمَ أَعْطَانِي اَلدَّنَانِيرَ أَوْ سِعْرَ يَوْمَ أُحَاسِبُهُ قَالَ "سِعْرَ يَوْمَ أَعْطَاكَ اَلدَّنَانِيرَ لِأَنَّكَ حَبَسْتَ مَنْفَعَتَهَا عَنْهُ".
Safwan narrated from Ishaq ibn Ammar, who said: I asked Abu Ibrahim (Imam Musa ibn Jafar Al-Kadhim عليه السلام) about a man who owes me money and repays me partially with dinars and partially with dirhams. When he comes to settle the remaining amount, the price of the dinars has changed. I asked: "Which price should I calculate, the price on the day he gave me the dinars or the price on the day we settle the account?" Imam عليه السلام said: "The price on the day he gave you the dinars, because you withheld their benefit from him."
- Ṣaḥīḥ al-Faqīh