Zakat (Kitab Al-Zakat)
Dawud :: Book 9 : Hadith 1705
Narrated Iyad ibn Himar:
The Prophet (peace_be_upon_him) said: He who finds something should call one or two trusty persons as witnesses and not conceal it or cover it up; then if he finds its owner he should return it to him, otherwise it is Allah's property which He gives to whom He will.