Al-Kāfi
Hadith 9492- عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ سَهْلِ بْنِ زِيَادٍ وَأَحْمَدَ بْنِ مُحَمَّدٍ جَمِيعاً عَنِ ابْنِ مَحْبُوبٍ عَنْ خَالِدِ بْنِ جَرِيرٍ عَنْ أَبِي الرَّبِيعِ قَالَ سُئِلَ أَبُو عَبْدِ اللهِ (عَلَيْهِ السَّلام) عَنْ رَجُلٍ أَقْرَضَ رَجُلا دَرَاهِمَ فَرَدَّ عَلَيْهِ أَجْوَدَ مِنْهَا بِطِيبَةِ نَفْسِهِ وَقَدْ عَلِمَ الْمُسْتَقْرِضُ وَالْقَارِضُ أَنَّهُ إِنَّمَا أَقْرَضَهُ لِيُعْطِيَهُ أَجْوَدَ مِنْهَا قَالَ لا بَأْسَ إِذَا طَابَتْ نَفْسُ الْمُسْتَقْرِضِ.
2. A number of our people have narrated from Sahl ibn Ziyad Ahmad ibn Muhammad from Ahmad ibn Muhammad all from ibn Mahbub from Khalid ibn Jarir from abu al-Rabi‘ who has said the following: “Once abu ‘Abd Allah (a.s.), was asked about the case of a man who gave a loan to another man who paid it back with better dirhams without compulsion, and the creditor knew it as well as the debtor that the loan was given to receive payment with the better dirhams. He (the Imam) said, it is not unlawful.’”