Something really significant happened in regard to the kingdom of God when Jesus came. When Jesus began his ministry he made this statement to Israel, "Repent for the kingdom of heaven is at hand." It is really a statement to Israel to turn, and repent for the kingdom of heaven is at hand. Things are changing in regard to the kingdom.
but as many as receiving him to them he gave the right to become children of God, the ones believing in his name, the ones born not from blood nor from fleshly will nor from a husband's will, rather from God (John 1:12-13)
I truly tell you, unless a person is born from above, he is not of the kingdom of God (John 3:3)Not of the kingdom of God is the same as saying not being children of God. Being born from above is the same as saying being born from God of the Spirit. What changed significantly in the new covenant is how one enters the kingdom of God; through being born anew.
... he gave the right to become children of God, the ones believing in his name, the ones born not from blood nor from fleshly will nor from a husband's will, rather from God (John 1:12-13)
Paul expresses this covenant God made with Abraham in this way, "now the promises made to Abraham and to his descendant did not say 'and to descendants' referring to many but to your descendant, referring to one who exists Christ" (Galatians 3:16). So the promise was to bless peoples of all nations through Christ. The Mosaic Law which came some four hundred years after the promise God made to Abraham does not annul the covenant previously established by God to make it void. The promise was given before the Law and before circumcision of the flesh thus they do not rest upon these things. The promise was given before so it is from faith according to grace, therefore those who share the faith of Abraham are sons of Abraham, as it was written "I have made you the father of many nations" (Romans 4:16-21).
Now, faith is the opposite of earthly and fleshly things, it is believing in a God that makes alive the dead and brings into existence that which does not exist. This is the faith of Abraham, Paul writes, who believed these things about God. In the gospel God brings into existence a new creation in Christ, something that did not exist before.
Blessed be the God and Father of our Lord Jesus Christ! According to his great mercy, he has caused us to be born into a living hope through the resurrection of Jesus Christ from the dead, ( 1 Peter 1:3 ESV)
Now, Abraham looked into this new covenant by which new birth into the kingdom of God would come thus Paul writes the gospel was preached to him beforehand, "Know then that it is from faith those who are the sons of Abraham. And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, 'In you shall all the nations be blessed.' So then, those who are of faith are blessed along with Abraham, the man of faith" (Galatians 3:6-9).
Even though Jesus had not yet died for the atonement of man's sin and to appease God's wrath and anger toward sinful man and though Jesus had not yet given men the right to become children of God through the new birth of the Spirit those from the old covenant were accounted righteous by their faith. In the new covenant there is no other way to God the Father as Jesus said, he is the only Way. There are no promises in the old covenant that bypass the new covenant, which was established in his blood. "For all the promises of God are yes in him, therefore through him our amen is to God for his glory" (2 Corinthians 1:20).
One can only enter the kingdom of God through being born anew of the Spirit. Becoming a new creation in Christ is a sign of our covenant, "For not a Jew existing that outwardly, not also of the circumcision in the flesh, rather a Jew is inwardly, also circumcision of the heart in Spirit not the written code, so that a person's praise comes not from man rather from God" (Romans 2:28-29). This puts emphasis on what Paul writes saying salvation is a gift from God, not of works lest we boast.
Self-righteousness and a works justification boasts in the fleshly man, not giving God the praise and honor and glory. If the status of being a child of God were based upon whether we were born fleshly a Jew under the Law we would have something to boast about, and others would have no hope of salvation being without God. But the good news of salvation comes to all peoples of all nations. The new birth says we are children of God as God's Spirit testifies with ours that he is our Father and we are his children (Romans 8: 15-16).
Just like wisdom and righteousness and redemption and sanctification come from Jesus, so we do not boast in ourselves, so also does entry into the kingdom of God, it comes to those who receive him and believe in his name, to them he gives the right to enter the kingdom of heaven, not born from a fleshly birth or human's will but from God.
The words of Jesus ring true to all people and all nations saying "You must be born from above to enter the kingdom of God." You must be born of the Spirit, to become a child of God, to enter the kingdom of God.