Genesis 4:15; Genesis 4:24

15 And the Lord said to him, It shall not be done so, but each man that shall slay Cain shall be punished sevenfold. And the Lord set a sign in Cain, that each man that should find him should not slay him. (And the Lord said to him, It shall not be done so, but any man who shall kill Cain shall be punished seven times. And the Lord put a mark on Cain, so that any man who would find him would not kill him.)

24 (if) vengeance shall be given sevenfold of Cain, forsooth of Lamech seventy times seven times. (if vengeance shall be given seven times for Cain, then for Lamech it shall be seventy-seven times.)