Genesis 4:13-15

Cain said to the LORD, “My punishment is too great to bear! Behold, You have driven me this day from the face of the ground; and from Your face I will be hidden, and I will be a vagrant and a wanderer on the earth, and whoever finds me will kill me.” So the LORD said to him, “Therefore whoever kills Cain, vengeance will be taken on him sevenfold.” And the LORD appointed a sign for Cain, so that no one finding him would slay him.