Here is all one has to know:
Adam introduced sin into the world of mankind by one transgression, a physical deed of disobedience to God. Ro 5:12
At the same time death was entered into the world because death is the result of sin.
The concept of death must be properly understood as God defines it. It is separation and that is all it is.
The separation that took place when Adam sinned was the breath of life that was breathed into him by God departed, which was the Spirit of God.
This is the same Spirit that gives all believers in Jesus Christ and the work he did on our behalf on the cross and his resurrection, the permanent and never ending indwelling of God in our bodies, the Holy Spirit. this is eternal life.
The Holy Spirit is equated by God as the righteousness of Christ because he indwelt Christ in all but 3 hours of his life on earth and was his power in his flesh to please God in all things. Compare Jn 1:4 with Jn 3:34 & context.
Adam was charged with sin because he and his wife were one and the seed of humanity was in him.
Since the image of God was lost in Adam when he sinned, three-fold, soul, body, and Spirit, and Adam produce the family of man in his corrupted image, soul and body, the result was that there was no power over sins (deeds of the body that displeased God) and men eventually died physically when the soul and body were separated, each part going to a different place.
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How sin works to bring death;
James 1:13 Let no man say when he is tempted, I am tempted of God: for God cannot be tempted with evil, neither tempteth he any man:
14 But every man is tempted, when he is drawn away of his own lust, and enticed.
15 Then when lust hath conceived, it bringeth forth sin: and sin, when it is finished, bringeth forth death.
16 Do not err, my beloved brethren. (read and consider the context)
Sin is a deed done in the body. All men are guilty of their own sins. All men will be judged according to their sins. As long as men have their sins charged to them they are condemned to die the second death, which is eternal separation of the soul and body from the presence of God in the lake of fire. The only thing that will take away the condemnation is if sin is somehow removed from the person and the law is satisfied by a prosecution that is demanded of the law.
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The Judge has put out a timeless notice that sins have been taken away by a man without any sin of his own, God's (the gracious Judge) own own son has died as sin to put it away for everyone so the guilty can be reconciled if they will come for pardon by the Judge in his name, Jesus name. Since there are no personal sins to hold him the Judge raised Jesus from the dead and gave his life, the Spirit of God, who is eternal, to live in the bodies of those who receive the gracious offer of the Judge to come.
2 Cor 5:19 To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation.
20 Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ's stead, be ye reconciled to God.
21 For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.
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The magnitude of the sacrifice;
Jn 1:29 The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world.
When?
He 9:24 For Christ is not entered into the holy places made with hands, which are the figures of the true; but into heaven itself, now to appear in the presence of God for us:
25 Nor yet that he should offer himself often, as the high priest entereth into the holy place every year with blood of others;
26 For then must he often have suffered since the foundation of the world (kosmos): but now once in the end of the world (aion - of law) hath he appeared to put away sin by the sacrifice of himself.
What does that do for sinners?
2 Cor 5:18 And all things are of God, who hath reconciled us to himself by Jesus Christ, and hath given to us the ministry of reconciliation;
19 To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation.
How long will this last?
He 9:27 And as it is appointed unto men once to die, but after this the judgment: (while a sinner is alive on the earth)
There is an end to grace as the operative principle of God's divine dealing with sinners:
Acts 17:29 Forasmuch then as we are the offspring of God, we ought not to think that the Godhead is like unto gold, or silver, or stone, graven by art and man's device.
30 And the times of this ignorance God winked at; but now commandeth all men every where to repent:
31 Because he hath appointed a day (this is the day of the LORD), in the which he will judge the world in righteousness by that man whom he hath ordained; whereof he hath given assurance unto all men, in that he hath raised him from the dead.
Jesus Christ died for sinners to pay the penalty for our sins and God accepted his payment and we can be assured of that by the fact that God raised Jesus from the dead. Anything that takes away from this fact is not the gospel that will save a soul from the second death.