Sayyiduna Abu Rafi' (may Allah be pleased with him) says: The Messenger of Allah (peace and blessings be upon him) took a young camel as a salaf, that is, as a loan. When camels of charity came to him (peace and blessings be upon him), he (peace and blessings be upon him) ordered me to give the man a camel in return for his camel. I said to him (peace and blessings be upon him): "Among the charity camels, all are better than that one." He (peace and blessings be upon him) said: "Give him a good camel, for the best people are those who are best in paying back what is due."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11097