It is narrated from Sayyiduna Amir bin Rabi'ah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "(An injury caused by) an animal is not compensated, (harm from falling into) a well is not compensated, and on buried treasure (rikaz) there is a fifth (khumus, as zakah)."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Layth bin Sa'd except Ya'qub bin Ibrahim."
Hadith Referenceالمعجم الأوسط / باب العين / 3928
Hadith Takhrij«أخرجه النسائي فى «السنن الكبرى» برقم: 5801، والبزار فى «مسنده» برقم: 3824، والطبراني فى «الأوسط» برقم: 6968»