Cain wasn’t put to death for murder
But the entire world was - at the flood.
The point with Cain is that God said he needed to battle against sin. Then he was punished with banishment.
Without the law there is no such thing as sin for "
sin is transgression of the law" 1 John 3:4
God said that the penalty for eating of the tree of knowledge of evil was death - yet they did not die that very day. It does not mean the law did not exist or that rebellion was not sin for them or that it would have no consequence.
, which is the penalty given by the law - because that law didn’t exist, and wouldn’t, until given to Moses 430 years after Abraham.
In Genesis 9 God sets the penalty for murder as death.
Gen 9:
5 I certainly will require your lifeblood; from every animal I will require it. And from
every person, from every man
as his brother I will require the life of a person.
6 Whoever sheds human blood,
By man his blood shall be shed,
For in the image of God
He made mankind.
Cain was instead exiled. Being exiled is not the penalty for murder
It was the penalty God set for Cain's sin.
You are mixing up God physically killing sinners, with God imputing their sins to them on judgment day and sending them to hell.
God said that "the soul that sins must die" Ezek 18:4 and that all the world - every single person has sinned as God sees it.. Rom 6:23 just as God accused Cain of failing to battle against sin in his day.
Rom 3:19-20 says all are informed as to their sin and penalty and guilt - with every mouth closed.
Rom 1 says even godless pagans with no access to scripture at all are convicted by God's Law.
There was never a time when God did not recognize "taking His name in vain" - as sin.
Rom 1:
18 For the
wrath of God is revealed from heaven against all ungodliness and unrighteousness of people who suppress the truth in unrighteousness, 19 because that which is known about God is evident within them; for
God made it evident to them. 20 For since the creation of the world His invisible
attributes, that is, His eternal power and divine nature,
have been clearly perceived, being understood by what has been made, so that
they are without excuse. 21 For even though they knew God, they did not honor Him as God or give thanks, but they became futile in their reasonings, and their senseless hearts were darkened. 22 Claiming to be wise, they became fools, 23 and they
exchanged the glory of the incorruptible God for an image in the form of corruptible mankind, of birds, four-footed animals, and crawling creatures.
24 Therefore God gave them up to vile impurity in the lusts of their hearts, so that their bodies would be dishonored among them. 25 For they exchanged the truth of God for falsehood,
and worshiped and served the creature rather than the Creator, who is blessed forever. Amen.
26 For this reason God gave them over to degrading passions; for their women exchanged natural relations for that which is contrary to nature, 27 and likewise the men, too, abandoned natural relations with women and burned in their desire toward one another, males with males committing shameful acts and receiving in their own persons the due penalty of their error.
28 And just as they did not see fit to acknowledge God, God gave them up to a depraved mind, to do those things that are not proper, 29
people having been filled with all unrighteousness, wickedness, greed,
and evil; full of envy, murder, strife, deceit,
and malice;
they are gossips, 30 slanderers, haters of God, insolent, arrogant, boastful, inventors of evil, disobedient to parents, 31 without understanding, untrustworthy, unfeeling,
and unmerciful; 32 and although
they know the ordinance of God, that
those who practice such things are worthy of death, they not only do the same, but also approve of those who practice them.