It is narrated from Hazrat Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The blood of one who dies by falling into a well is wasted, the blood of one who dies in a mine or desert is also wasted, and for the buried treasure (found by someone), one-fifth (khums) is obligatory."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7120