Genesis 4:15-16

And the LORD said to him, “Therefore, whoever kills Cain, a sevenfold vengeance [that is, punishment seven times worse] shall be taken on him [by Me].” And the LORD set a [protective] mark (sign) on Cain, so that no one who found (met) him would kill him. [Gen 4:24] So Cain went away from the [manifested] presence of the LORD, and lived in the land of Nod [wandering in exile], east of Eden.