Modern medical ethics, in particular the principle of Non-Maleficent, advises the medical staff to avoid any harm to the patient. Islamic jurists, using religious texts and sources, have introduced rules that are applicable in many areas of life. Among these rules, is the rule Non-Harm, that in this article to review this rule and its applications in medicine. In addition to discussions of the documents, a better understanding of the words "Darar" and "Dirar" and deny or forbid the word "La" at the beginning of the base document, is one of the major issues and disputes. Organ transplants, family planning and birth control, responsibility to protect the health, need to see a doctor for treatment, civil responsibility for doctors in the treatment, responsibility for custodians of society for the control of AIDS, are the problems affecting today's health systems that the rule of No Harm is flowing in them.