Who are the sons/children of God mentioned here?
Romans 8:17 And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together. 18 For I reckon that the sufferings of this present time are not worthy to be compared with the glory which shall be revealed in us. 19 For the earnest expectation of the creature (or creation) waiteth for the manifestation of the sons of God. 20 For the creature was made subject to vanity, not willingly, but by reason of him who hath subjected the same in hope, 21 Because the creature itself also shall be delivered from the bondage of corruption into the glorious liberty of the children of God.
God created the earth for a purpose.
He created it to be inhabited and filled with his glory.
Isaiah 45:18 For thus saith the LORD that created the heavens; God himself that formed the earth and made it; he hath established it, he created it not in vain, he formed it to be inhabited: I am the LORD; and there is none else.
Numbers 14:21 But as truly as I live, all the earth shall be filled with the glory of the LORD.
God made man in his own image and his intention is to glorify man with his nature to live forever on the earth.
This is the way that God intends to fill the earth with his glory.
God made man with freewill so that he could choose to be part of God’s purpose or reject it.
The qualification is obedience.
Adam disobeyed God and brought sin and death upon himself and his descendants.
Sin is disobedience to God’s commandments.
Death is the punishment for sin.
Because Adam ate the fruit of the tree of the knowledge of good and evil, the propensity to sin passed on to his descendants.
All sin and all die.
Romans 5:12 Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned:
In order to save men and women from sin and death God fathered a son, Jesus Christ.
Jesus Christ lived a life without sin and gave himself as a sacrifice to redeem men and women from sin and death.
By his obedience Christ is able to save men and women, and their faith (or belief) in him is counted for righteousness.
Romans 5:19 For as by one man’s disobedience many were made sinners, so by the obedience of one shall many be made righteous.
During his ministry Christ preached the gospel of the kingdom of God.
The kingdom of God is to be established on the earth when Christ returns. All who want a part in it must repent of their sinful way of life and be baptised into Christ for the remission of their past sins.
After baptism we must live a new life by the commandments of Jesus Christ as found in the New Testament.
By being baptised we go from being ‘in Adam’ to being ‘in Christ’.
In Christ they become a new creature or creation.
2 Corinthians 5:17 Therefore if any man be in Christ, he is a new creature old things are passed away; behold, all things are become new.
We become sons of God in prospect.
1 John 3:2 Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.
Jesus Christ died not just for those who live after him, but also for those who lived before him, who had faith (believed) in God’s promise to provide a redeemer.
Both those who lived before Christ and those who live after are saved by faith.
By faith we become a new creature, part of a new creation which will be revealed when Christ returns to raise the faithful from the dead and give us immortality.
1 Corinthians 15:53 For this corruptible must put on incorruption, and this mortal must put on immortality.
Christ, in being raised from the dead with the divine nature is the firstborn of this new creation.
Colossians 1:15 Who is the image of the invisible God, the firstborn of every creature:
This creature (or creation) refers to men and women, not to animals.
Mark 16:15 And he said unto them, Go ye into all the world, and preach the gospel to every creature.
Colossians 1:23 If ye continue in the faith grounded and settled, and be not moved away from the hope of the gospel, which ye have heard, and which was preached to every creature which is under heaven; whereof I Paul am made a minister;
The return of Christ and the revealing of the sons of God (the faithful glorified) will usher in a new era upon the earth, when God’s will will be done on earth even as it is now done in heaven.
Matthew 6:10 Thy kingdom come. Thy will be done in earth, as it is in heaven.
All who understand the purpose of God live in hope of the promised fulfilment, when the sons of God will be revealed in glory at the return of Christ.
This hope makes the trials and suffering in this life bearable.
The fulfilment of God’s purpose is in two stages.
When Christ returns he will rule over the mortal population of the earth for 1000 years.
At the end of this millennial reign there will be a second resurrection and a final judgment.
Sin and death will be eradicated and all who live on will be given the divine nature.
God will live in them and with them forever.
Paul explains what is to happen:
1 Corinthians 15:20 But now is Christ risen from the dead, and become the firstfruits of them that slept. 21 For since by man came death, by man came also the resurrection of the dead. 22 For as in Adam all die, even so in Christ shall all be made alive. 23 But every man in his own order: Christ the firstfruits; afterward they that are Christ’s at his coming. 24 Then cometh the end, when he shall have delivered up the kingdom to God, even the Father; when he shall have put down all rule and all authority and power. 25 For he must reign, till he hath put all enemies under his feet. 26 The last enemy that shall be destroyed is death. 27 For he hath put all things under his feet. But when he saith all things are put under him, it is manifest that he is excepted, which did put all things under him. 28 And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all.
This time is described in Revelation
Revelation 21:3 And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God. 4 And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.
This will be the fulfilment of God’s purpose.
I hope you find this helpful.