Genesis 4:15 in the World English Bible
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.
Context
14 Behold, thou hast driven me out this day from the face of the earth; and from thy face shall I be hid; and I shall be a fugitive and a vagabond in the earth; and it shall come to pass, that every one that findeth me shall slay me.
15 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.
16 And Cain went out from the presence of the LORD, and dwelt in the land of Nod, on the east of Eden.