Musnad Ahmad 30:2247

'Affan narrated to us, Shu'bah narrated to us, from Muhammad ibn Ziyad, who said: I heard Abu Hurairah, from the Prophet, peace and blessings of Allah be upon him, who said: "The injury caused by an animal (al-'ajma') is exempt from liability (jubar), the mine is exempt from liability (jubar), and the well is exempt from liability (jubar), and in buried treasure (al-rikaz) there is one-fifth."