Sayyiduna Ibn Umar (may Allah be pleased with them both) narrates from Sayyiduna Amir bin Rabi'ah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "A wound caused by an animal carries no compensation, (an accident in) a well carries no compensation, a mine carries no compensation, and in rikaz (buried ancient treasure) there is one fifth (khumus)."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Bukayr bin Abdullah (may Allah have mercy on him) except Mu'adh Abu Bakr (may Allah have mercy on him), and his son is alone in narrating it from him."
Hadith Referenceالمعجم الأوسط / باب الميم / 6968
Hadith Takhrij«أخرجه النسائي فى «السنن الكبرى» برقم: 5801، والبزار فى «مسنده» برقم: 3824، والطبراني فى «الأوسط» برقم: 3928»