Genesis 4:13-15

Cain replied to the LORD, “My punishment is too great for me to bear! You have banished me from the land and from your presence; you have made me a homeless wanderer. Anyone who finds me will kill me!” The LORD replied, “No, for I will give a sevenfold punishment to anyone who kills you.” Then the LORD put a mark on Cain to warn anyone who might try to kill him.