Genesis 4:24

If Cain shall be avenged sevenfold, truly Lamech seventy and sevenfold.

The verse belongs to the fourth chapter of Genesis that tells the whole story of Cain, his family and his descendants. Those descendants are presented as corrupt and wicked, and it is from them that Enoch separated himself. God in mercy spared Cain's life even though his murder merited death, giving him opportunity for repentance. Cain lived only to harden his heart and rebel against divine authority, becoming the head and tempter of bold, abandoned sinners.

Lamech, the fifth in descent from Cain, added polygamy to the murder begun by Cain and then boastfully defied God, acknowledging Him only to claim safety for himself. He took the vengeance promised in Cain's case and twisted it into an assurance of far greater protection for his own violence. His line was distinguished by mere earthly and material progress yet was regardless of God and opposed to His purposes, seeking possessions and enjoyment in the earth under the curse of sin at the head of those who worship the god of this world.

The example and demoralizing influence of Cain's line spread departure from God's plain commands until the world was filled with transgression, corruption and violence, calling for its destruction by God. Sparing the first murderer set a lesson before the whole universe bearing on the great controversy, showing what would result from letting the sinner live forever to carry out rebellion against God. God's forbearance only made the wicked more bold and defiant, reaching its fruition fifteen centuries after the sentence on Cain in the crime and pollution that flooded the earth. This made manifest that the sentence of death on the fallen race for transgressing God's law was both just and merciful. The longer men lived in sin the more abandoned they became, so the divine sentence cutting short a career of unbridled iniquity and freeing the world from hardened rebels was a blessing rather than a curse.