How does God make this justice happen?
Genesis 4:15
And the Lord said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And the Lord set a mark upon Cain, lest any finding him should kill him.
Genesis 4:24
If Cain shall be avenged sevenfold, truly Lamech seventy and sevenfold.
If an unrepentant killer goes to hell forever and an unrepentant killer of a killer goes to hell forever, how then can the punishment that God promises be fulfilled?
How can God give punishment seven times forever or seventy times forever?
Regards
DL
As others have pointed out, the text says nothing of "hell", but of "vengence".
But the main point of the OP seems to be the "sevenfold". This is a Hebrew idiom relating to perfection or completeness. It is not to be taken as a literal numeric value. According to the study note in the NET Bible on Gen 4:15:
The symbolic number seven is used here to emphasize that the offender will receive severe punishment. For other rhetorical and hyperbolic uses of the expression “seven times over,” see Pss 12:6; 79:12; Prov 6:31; Isa 30:26.
The study note on Gen 4:24 may help, too:
Seventy-seven times. Lamech seems to reason this way: If Cain, a murderer, is to be avenged seven times (see v. 15), then how much more one who has been unjustly wronged! Lamech misses the point of God’s merciful treatment of Cain. God was not establishing a principle of justice when he warned he would avenge Cain’s murder. In fact he was trying to limit the shedding of blood, something Lamech wants to multiply instead. The use of “seventy-seven,” a multiple of seven, is hyperbolic, emphasizing the extreme severity of the vengeance envisioned by Lamech.