Genesis 4:15 in the King James Version
And the LORD said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And the LORD set a mark upon Cain, lest any finding him should kill him.
Context
14 Behold, you have driven me out today from the surface of the ground. I will be hidden from your face, and I will be a fugitive and a wanderer on the earth. Whoever finds me will kill me.”
15 The LORD said to him, “Therefore whoever slays Cain, vengeance will be taken on him sevenfold.” The LORD appointed a sign for Cain, so that anyone finding him would not strike him.
16 Cain left the LORD’s presence, and lived in the land of Nod, east of Eden.