Sayyiduna Abu Rafi’ (may Allah be pleased with him), the freed slave of the Messenger of Allah (peace and blessings be upon him), said: The Messenger of Allah (peace and blessings be upon him) took a young camel as a loan. When the camels for charity (zakat) arrived, Sayyiduna Abu Rafi’ (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) ordered me to return the man’s camel. I said: I have not found among these camels except a best four-toothed (mature) camel. The Messenger of Allah (peace and blessings be upon him) said:“Give him that best four-toothed camel; the best people are those who repay debts well.”
Imam Darimi (may Allah have mercy on him) said: This hadith strengthens the statement of those who consider the sale of an animal in exchange for another animal to be permissible.