Genesis 4:24

24 If Cain is avenged seven times, then Lamech seventy-seven times.”

Read Genesis 4:24 Using Other Translations

If Cain shall be avenged sevenfold, truly Lamech seventy and sevenfold.
If Cain's revenge is sevenfold, then Lamech's is seventy-sevenfold."
If someone who kills Cain is punished seven times, then the one who kills me will be punished seventy-seven times!”