Amr bin Shu'aib narrates from his father, who narrates from his grandfather, that the Prophet (peace be upon him) said regarding the treasure which a man found in a deserted land of the pre-Islamic period: "And if you found it in a populated town or on a public road, then announce it, and if you found it in a deserted place of the pre-Islamic period or an uninhabited settlement, then there is a fifth in it and in buried treasure."
Hadith Referenceمسند الإمام الشافعي / كتاب الزكاة / 730
Hadith Takhrijصحيح من غير هذا الطريق اخرجه ابوداود، اللقطة، باب التعريف بالقطة (1710) ۔ واحمد: 2/ 180 ، 186 ، 203 ، 208 وصححه ابن خزيمة (2327)، (2328) وابن الجارود (670) ۔ والحاكم: (2/ 65)۔