Genesis 4:24

Sevenfold vengeance shall be taken for Cain, but for Lamech seventy-sevenfold. Sevenfold vengeance was taken for Cain, as he bore the penalties of fratricide and envy as a wandering fugitive up to the seventh generation. But for Lamech seventy-sevenfold, because, as Jerome testifies, reported to him by the Hebrews, and Josephus confirms the same, seventy-seven souls were generated from the lineage of Cain, which perished in the flood. They say that in this number the vengeance upon Lamech was accomplished, as his lineage persisted until the flood. Lamech is interpreted as "Smiting" or "Smitten," both interpretations fitting the same man who struck Cain and for this same parricide he was struck by divine vengeance. Mystically, however, Lamech signifies mankind, both smitten by the deceit of the ancient enemy in the first parent, and smiting itself by the accumulation of daily sins, for which vengeance was given seventy-sevenfold; because until the advent of Christ, who appeared in the world in the seventy-seventh generation, the guilt of the first transgression pressed upon mankind, until He came to take away the sins of the world, and by the door of the kingdom of heaven, opened by his baptism or passion, lead us into eternal life which we lost in Adam. Then, therefore, vengeance upon Lamech ceased because, with the sting of death and sin broken by the Lord's passion and resurrection, mankind returned to the heavenly kingdom.

DID LAMECH KILL CAIN, AS SOME THINK? — It is a false opinion based on what Lamech says of Cain, I killed a man who hurt me, a young man who covered me with wounds (Gen. 4:23). For Lamech was born of the fifth generation after Cain, that is, of Methuselah, the great grandson of Cain. Lamech recalls this fact to show that a much more rigorous punishment was reserved for those who would bound since the promulgation of the law. If, then, after Cain, the punishment has been sevenfold for the imitator of his crime, how much more severe will this chastisement be for that which neither the crime of Cain nor the severe reproaches addressed to him, nor the sentence pronounced against him may have diverted from a crime in which impiety is joined to cruelty. Lamech has committed this homicide after Cain, and without a doubt, from what we have said. His punishment was seven times more severe. Now what will happen to him who, after Lamech, will follow his example? He tells us by saying, I will avenge the death of Lamech seventy times seven times (Gen. 4:24). If this criminal action is not followed by repentance, it will be punished with a punishment seventy times seven times more terrible. That is why our Lord commands to forgive him who has sinned this same number of times, if he regrets his faults. (Mt. 18:22) But it must not be believed that another homicide was committed before that of Lamech and after that of Cain, because Lamech says, The murder of Cain was avenged (Gen. 4:24 LXX), as if this vengeance was done. As for Lamech, how could he have said that he had already been the object of this vengeance, whereas the murder he confessed to have committed was still recent? It may therefore be said that every crime carries with it its condemnation. For when there is no other hope, besides that one knows what is worth an act which is consummated, one considers as already done a thing which is yet to be done. Finally, it was said to Adam and Eve: The day that you eat of this fruit, you shall die of death (Gen. 2:17), and yet they did not die immediately, but after a long interval of time. However, since they had already lost the hope of immortality, death, which was not to strike them until later, was, so to speak, present to them, because it was then the object of their fears. When, therefore, Lamech confesses to having killed a young man, since it is certain that Cain…