'Imran b. Husain reported God’s Messenger as saying, “When anyone has something due to him from another he will be credited with sadaqa for every day he allows the other to postpone payment.”
وَعَن عبد الله بن أبي ربيعَة قَالَ: اسْتَقْرَضَ مِنِّي النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَرْبَعِينَ أَلْفًا فَجَاءَهُ مَالٌ فَدَفَعَهُ إِلَيَّ وَقَالَ: «بَارَكَ اللَّهُ تَعَالَى فِي أَهْلِكَ وَمَالِكَ إِنَّمَا جَزَاءُ السَّلَفِ الْحَمْدُ وَالْأَدَاءُ» . رَوَاهُ النَّسَائِيُّ
‘Abdallah b. Abu Rabi'a said the Prophet borrowed forty thousand* from him, and when revenue came in he paid it to him saying, “God most high bless your family and your property! The only reward for a loan is commendation and repayment.”
*The text mentions the number. It probably means dirhams.
My brother died leaving three hundred dinars and some young children, and I wanted to use them for their maintenance, but God’s Messenger said to me, “Your brother is im-prisoned by his debt, so pay it on his behalf.” I went and did so, and returned to tell God’s Messenger that I had done it and that there remained only a woman who claimed two dinars but had no proof she could show. He replied, “Give them to her, for she is speaking the truth.”