Genesis 9:6

Whoso sheddeth man’s blood. God would avenge or inflict punishment for every murder, not directly, however, as He did in the case of Cain, but indirectly, by placing in the hand of man judicial power. The word “sheddeth” implies willful murder and not an accidental taking of life, manslaughter, for which the law made other provisions than those mentioned here (Num. 35:11). The divine injunction endows temporal government with judicial power, and places in its hand the sword. God took care to erect a barrier against the supremacy of evil, and thus laid the foundation for an orderly civil development of humanity.