Sunan an-Nasa'i 4618

It was narrated that Abu Hurairah said:"A man had lent a camel of a certain age to the Prophet and he came to get it back. He said: "Give it to him" But they could only find a camel that was older than it. He said: "Give it to him." He said: "You have repaid me well," The Messenger of Allah said; "The best of you is the one who is best in repaying