Musnad Abu Ya'la al-Mawsili 155:235

Zakariya ibn Yahya narrated to us, Hushaym narrated to us, from Hisham, from Ibn Sirin, from Abu Hurayrah, who said: The Messenger of Allah (ﷺ) said: "The injury caused by an animal (al-'ajma') is exempt from liability (jubar), and the well is exempt from liability (jubar), and the mine is exempt from liability (jubar)." "And in the buried treasure (al-rikaz), there is one-fifth."