Sahih Muslim Book 18, Hadith Number 4276.

Chapter : Stray thing found by anyone.

Zaid b. Khalid al-Juhani, the Companion of Allah’s Messenger (may peace be upon him), said that Allah’s Messenger (may peace be upon him) was asked about the picking up of stray gold or silver, whereupon he said: Recognise well the strap and the bag (containing) that and then make an announcement regarding that for one year, but if none recognises it, then spend that and it would be a trust with you; and if someone comes one day to make demand of that, then pay that to him. He (the inquirer) asked about the lost camel, whereupon he said: You have nothing to do with that. Leave that alone, for it has feet and also a leather bag, it drinks water, and eats (the leaves) of the trees. He asked him about sheep, whereupon he said: Take it, it is for you, or for your brother, or for the wolf.