Musnad Ahmad 33:693

Khalaf ibn al-Walid narrated to us, 'Abbad ibn 'Abbad narrated to us, from Mujalid, from al-Sha'bi, from Jabir ibn 'Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The grazing livestock is 'jabar' (liable for no compensation), the well is 'jabar', and the mine is 'jabar', and in the 'rikaz' (buried treasure) is one-fifth." He said: And al-Sha'bi said: "The 'rikaz' is the ancient treasure."