Codes, oaths and prayers guiding health practitioners in caring for patients have been extant for centuries. Codes of ethics have been expressed in the form of prayers, oaths, creeds, institutional directives, and statements.
"Prayers state a very personal commitment of duty; oaths publically pledge the oath taker to uphold specified responsibilities; and codes provide more comprehensive standards to guide the practicing health practitioner, patient, or other decision maker. Each form of ethical statement implies a moral imperative, either to be accepted by the individual personally or to be enforced by a practitioner organization, religious community, or governmental body."
--- Veatch, Robert. 1995. "Medical Codes and Oaths." Vol. 1, pp. 1419-1435, Encyclopedia of Bioethics, 2nd ed. New York:Macmillan.