Genesis 4:19 - Coke's Commentary on the Holy Bible

Lamech took unto him two wives, &c.— This account of Lamech has been the subject of much inquiry; and indeed it is very difficult to be understood. "That Lamech had used force against some other man," says Dr. Delaney, "is evident: as also that he thought himself much more criminal in doing so, even than Cain; as appears from the words, if Cain shall be, &c." Now the true reason why God guarded Cain from destruction, under so severe a penalty upon any one who should slay him, was demonstrably this: that he might preserve him, as a living monument of the curse of God upon murder. Granting this to be the reason, and that Lamech knew it, (as he could not but know it,) his exclamation to his wives is plainly a confession that he had been guilty of a much greater crime than Cain; and therefore concluded, that God might justly render him a much more dreadful monument of his wrath than he had rendered Cain; and in this terror, that bitter exclamation falls from him, if Cain shall be avenged seven-fold, truly Lamech seventy and seven.