Sahih Muslim Book 18, Hadith Number 4273.

Zaid b. Khalid al-Juhani reported that a person asked Allah’s Apostle (may peace be upon him) about picking up of stray articles, whereupon he said: Make announcement about it for a year, and recognise well the strap and the bag (containing that); then spend that; and if its owner comes, make him the payment of that. He (the inquirer) said: Messenger of Allah, what about the lost goat? he said: Take it, for that is yours or for your brother, or for the wolf. He (again) said: (What about) the lost camel? The Messenger of Allah (may peace be upon him) was enraged until his cheeks became red (or his face became red) and then said: You have nothing to do about that; it has feet and a leather bag (to quench its thirst) until its owner finds it.