It is narrated from Sayyiduna Iyad bin Himar (may Allah be pleased with him) that he asked the Prophet (peace and blessings be upon him) about a luqatah (found property), and he (peace and blessings be upon him) said: "It should be announced, and it should not be hidden or concealed. If its owner comes, give it to him; otherwise it is the wealth of Allah, which He gives to whomever He wills."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15056