Genesis 4:13-15

4:13 Then Cain said to the Lord, “My punishment is too great to endure! 4:14 Look! You are driving me off the land today, and I must hide from your presence. I will be a homeless wanderer on the earth; whoever finds me will kill me.” 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.