It's interesting Just-me, in examining the scriptures regarding enmity, As Paul stated, the natural mind is not subject to the law of God, neither indeed can it be. The bible gives examples throughout of both the natural/carnal and spiritual/heavaenly state or mankind
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.1 Corinthians 15:45 And so it is written, The first man Adam was made a living soul; the last Adam was made a quickening spirit.
Psalms 119:154 Plead my cause, and deliver me: quicken me according to thy word.
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I was considering passages in the bible from before the Law was delivered to Moses, and well beyond that point, on through to the book of Revelations.
Before the time of Moses, there are clear examples of how "enmity," of the carnal man that is contrary to God, brought on destruction.
Starting from Adam and Eve sin entered the world, and there were consequences to that disobedience. Then we come to the time of Noah, (the law still hasn't been delivered to Moses) yet there are consequences for the entire earth.
Genesis 6:5 And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.
Genesis 6:8 But Noah found grace in the eyes of the LORD.
There was a standard set for what "wickedness," is, and a judgment that resulted in the whole earth being destroyed, all but Noah and his family. (Eight souls.)
Then on to the tower of Babel:
They were building a city with their own hands:
Genesis 11:4 And they said, Go to, let us build us a city and a tower, whose top may reach unto heaven; and let us make us a name, lest we be scattered abroad upon the face of the whole earth.
Genesis 11:5 And the LORD came down to see the city and the tower, which the children of men builded. Genesis 11:6 And the LORD said, Behold, the people is one, and they have all one language; and this they begin to do: and now nothing will be restrained from them, which they have imagined to do.
In the account when the whole earth was destroyed during the time of Noah, God said a very similar thing regarding Babel, "the imagination of the thoughts of man's heart was wicked continuously," "And now nothing will be restrained from them which they have imagined to do."
This also reminds me of what Jesus said, about the last days, "because iniquity will abound, the love of many will wax cold."
As with the time of Noah, and Babel, uncontrolled sin would wax worse and worse...and so they were scattered over the whole face of the earth.
Sodom and Gomorrah is another example.
Both cities were destroyed because sin was so great in the land. The Law had not yet been given to Moses, yet the cities came under judgment and were destroyed.
Genesis 18:20 And the LORD said, Because the cry of Sodom and Gomorrah is great, and because their sin is very grievous;
Again, that is an example that there was already a standard in place for what "sin," is..and judgment based on those things.
In the book of Revelations, through the tribulation there are many of the same examples. "Yet they would not repent," One example:
Revelation 9:20 And the rest of the men which were not killed by these plagues yet repented not of the works of their hands, that they should not worship devils, and idols of gold, and silver, and brass, and stone, and of wood: which neither can see, nor hear, nor walk:
To sum this up:
The promise made to Abraham was that all the nations of the earth would be blessed. The blessings come by the way of faith and faithfulness, as shown throughout the word.
To Abraham's natural seed the Law was given, which set His standard for the People who are "called by His name."
Israel was to be a light to the world, in show of righteousness and righteous judgement. As God is completely righteous and just.
The promise came through the birth, life, death and resurrection of Christ, that in HIM (and only in HIM) we would overcome this world.
We are changed in Christ, "behold all things become new."
Thus begins the process of the renewing of the mind going from from the milk of the word to the meat of the word, (being hearers of the word to being doers of the word, and overcoming sin in Christ by His power.) Through faith in Jesus. He overcame the world.
"The carnal mind is not subject to the Law of God, neither indeed can it be."
John 16:33 These things I have spoken unto you, that in me ye might have peace. In the world ye shall have tribulation: but be of good cheer; I have overcome the world.
Revelation 3:21 To him that overcometh will I grant to sit with me in my throne, even as I also overcame, and am set down with my Father in his throne.
1 John 5:4 For whatsoever is born of God overcometh the world: and this is the victory that overcometh the world, even our faith.
There are so many more examples, even in entering the promised land, and the events that followed as recorded in scripture throughout. I did attempt to keep this short but couldn't do so without showing some examples. There are many more...
As you stated, the enmity ceases in Christ through grace, so that in Him we can overcome this world.
Ephesians 5:27 That he might present it to himself a glorious church, not having spot, or wrinkle, or any such thing; but that it should be holy and without blemish.