Muwatta Imam Malik (Riwayat Ibn al-Qasim)

And with this chain (it is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him) that the Messenger of Allah, peace and blessings be upon him, said: "The injury caused by livestock is without liability (i.e., there is no blood money or penalty upon its owner), and (any injury or death) in a mine is without liability (i.e., there is no blood money or penalty upon its owner), and a well is without liability (i.e., if someone falls into a well, there is no blood money or penalty upon its owner), and in the case of a buried treasure (when found), one-fifth (must be set aside for Allah)."