I know people are citing Christianity a ton which has huge part in it but the concept is way older.
The Hippocratic Oath already touches on the subject: “I will use those dietary regimens which will benefit my patients according to my greatest ability and judgment, and I will do no harm or injustice to them.[4] Neither will I administer a poison to anybody when asked to do so, nor will I suggest such a course. Similarly I will not give to a woman a pessary to cause abortion.”.
The concept is way older and tons of medics still take that oath