Genesis 4:15

4:15 But the Lord said to him, “All right then, if anyone kills Cain, Cain will be avenged seven times as much.” Then the Lord put a special mark on Cain so that no one who found him would strike him down.

Genesis 4:24

4:24 If Cain is to be avenged seven times as much,

then Lamech seventy-seven times!”

Numbers 35:19

35:19 The avenger of blood himself must kill the murderer; when he meets him, he must kill him.

Romans 13:4

13:4 for it is God’s servant for your good. But if you do wrong, be in fear, for it does not bear the sword in vain. It is God’s servant to administer retribution on the wrongdoer.