Mukhtasar Bukhari (Abridged) 763 — One-fifth is obligatory on buried

Narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no compensation for injury caused by an animal, nor for one who falls into a well, nor for one who dies while working in a mine. However, there is a fifth (share) on treasure found (in the ground)."