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) borrowed a young camel, and then camels of charity came to him. Abu Rafi' (may Allah be pleased with him) said: So the Messenger of Allah (peace and blessings be upon him) ordered me to repay the man his debt. I got up, but found among the camels only fine camels in their fourth year. The Messenger of Allah (peace and blessings be upon him) said: "Give him that, for the best of Muslims is the one who repays his debt in the best manner."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 909