Volume 2 · Book 24 · Hadith 575
Narrated Abu Huraira Allah's Apostle said, "There is no compensation for one killed or wounded by an animal or by falling in a well, or because of working in mines; but Khumus is compulsory on Rikaz."
— Sahih Bukhari, Volume 2, Book 24: Obligatory Charity Tax (Zakat), Hadith #575