Sahih Bukhari Volume 3, Book 40, Hadith Number 560.

Narated By Zaid bin Khalid : A man came to Allah’s Apostle and asked about Al-Luqata (a fallen thing). The Prophet said, “Recognize its container and its tying material and then make a public announcement about it for one year and if its owner shows up, give it to him; otherwise use it as you like.” The man said, “What about a lost sheep?” The Prophet said, “It is for you, your brother or the wolf.” The man said “What about a lost camel?” The Prophet said, “Why should you take it as it has got its water-container (its stomach) and its hooves and it can reach the places of water and can eat the trees till its owner finds it?”