Abu Salamah narrates from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) took a two-toothed camel (as a loan), and the Prophet (peace and blessings be upon him) returned a camel older than it. He (peace and blessings be upon him) said: "The best of you is the one who is best in repaying a debt."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10949