Sahih Bukhari Volume 8, Book 73, Hadith Number 133.

Narated By Zaid bin Khalid Al-Juhani : A man asked Allah’s Apostle about “Al-Luqata” (a lost fallen purse or a thing picked up by somebody). The Prophet said, “You should announce it publicly for one year, and then remember and recognize the tying material of its container, and then you can spend it. If its owner came to you, then you should pay him its equivalent.” The man said, “O Allah’s Apostle! What about a lost sheep?” The Prophet said, “Take it because it is for you, for your brother, or for the wolf.” The man again said, “O Allah’s Apostle! What about a lost camel?” Allah’s Apostle became very angry and furious and his cheeks became red (or his face became red), and he said, “You have nothing to do with it (the camel) for it has its food and its water container with it till it meets its owner.”