Exodus 20:13 - Ellicott's Commentary On The Whole Bible

Thou shalt not kill. — From the peculiar duties owed by children to their parents, the Divine legislator went on to lay down those general duties which men owe to their fellow-men. And of these the first is that of respecting their life. The security of life is the primary object of government; and it has been well said that men originally coalesced into States with a view to self-preservation (Arist., Pol. i. 1). All written codes forbid murder; and in communities which are without written codes an unwritten law condemns it. When God “set a mark upon Cain” (Genesis 4:15), He marked thereby His abhorrence of the murderer. The “seven precepts of Noah” included one which distinctly forbade the taking of human life (Genesis 9:6). In all countries and among all peoples, a natural instinct or an unwritten tradition placed murder among the worst of crimes, and made its penalty death. The Mosaic legislation on the point was differenced from others principally by the care it took to distinguish between actual murder, manslaughter (Exodus 21:13), death by misadventure (Numbers 35:23), and justifiable homicide (Exodus 22:2). Before, however, it made these distinctions, the great principle of the sanctity of human life required to be broadly laid down; and so the law was given in the widest possible terms — “Thou shalt not kill.” Exceptions were reserved till later.