In Islam, prophetic medicine is the advice regarding sickness, treatment and hygiene based on reports of the Islamic prophet Muhammad as found in the hadith. The therapy involves diet, bloodletting, and cautery, and simple drugs, numerous prayers and pious invocations for the patient to perform, but no surgery. Maladies discussed include fevers, plague, leprosy, poisonous bites, protection from night-flying insects and the evil eye, rules for coitus, theories of embryology, etc. The authors of its manuals were religious clerics who collected and explicated these traditions, not physicians, and it is usually practiced by non-physicians. How much of the medicine is divine revelation and how much folk practices inherited from ancestors is disputed.