Sahih Bukhari Volume 3, Book 38, Hadith Number 501.
Narated By Abu Huraira : The Prophet owed somebody a camel of a certain age. When he came to demand it back, the Prophet said (to some people), “Give him (his due).” When the people searched for a camel of that age, they found none, but found a camel one year older. The Prophet said, “Give (it to) him.” On that, the man remarked, “You have given me my right in full. May Allah give you in full.” The Prophet said, “The best amongst you is the one who pays the rights of others generously.”