The Gospel Preached Beforehand
The promise "In you shall all the nations be blessed" was given to Abraham before circumcision and the Law thus does not rest on earthly birth and lineage, nor the Mosaic Law, but is according to grace so that it comes to people of all nations (Romans 4:15-16). In the Old Testament the chosen people were of earthly descendants, of Israel, but even then Paul writes not all were of the children of the promise, some were unbelievers as they were destined to be.*
"the ones from belief, are blessed together with Abraham, of faith" -- Galatians 5:19
In the New Testament we see the chosen people of the promise, and gospel which was preached to Abraham beforehand, comes to fruition in Christ and all people of all nations who believe are blessed along with Abraham. Just as the scriptures say, "the promises of God are yes and amen in Christ."
This is a key principle in Christian theology, found in 2 Corinthians 1:20, signifying that Jesus Christ is the confirmation and fulfillment of all God's promises. Jesus is the "descendant" of Abraham through whom the promises would come. Thus Christians respond with "Amen" to affirm belief in God's promise and faithfulness to fulfill them in Christ who is the author and perfecter of our faith.
In the New Testament we see that the distinction of the children of God is that they are of the faith of Abraham, Galatians 3:7-9, and they are born of God, of the Spirit, so they receive the promised Holy Spirit. Jesus came to redeem mankind and be a atone atonement and propitiation for sin but he also came to give the children of the promise the authority to be born of God, John 1:12-14.
The chosen of God, are predestined for adoption as his own, Ephesians 1:4-5, and the Spirit is one of Adoption testifying we are his, Romans 8:15-17, we are sealed or marked by the Spirit as a guarantee of our inheritance (Ephesians 1:13-14). Those of the Old Testament were counted righteous by their faith but were not born of the Spirit, which is what we are in Christ, a new creation. We of the new testament have a better covenant established by the death and blood of Jesus, and we receive the promises of God, including the promised Holy Spirit that is a guarantor of our inheritance.
"For a person is not a Jew who is one outwardly, and true circumcision is not something visible in the flesh. On the contrary, a person is a Jew who is one inwardly, and circumcision is of the heart—by the Spirit, not the letter. That man’s praise is not from men but from God." -- Romans 2:28-29.Faith is more than mere belief; it is complete trust and confidence in God and His promises. Throughout Scripture, numerous examples illustrate faith. Abraham, known as the father of faith, demonstrated belief in God when he obediently left his homeland (Genesis 12:1-4) and was willing to sacrifice his son Isaac (Genesis 22:1-18). His faith was credited to him as righteousness (Romans 4:3).
Abraham also had unbelief, God promised to have a son through his wife Sarah but she was barren so he attempted to have a son outside of God's promise, to bring about the fulfillment of God's will on his own. But as Paul writes Abraham did not judge according to his unbelief but was strengthened in his faith until he was full convinced in what God promised (Romans 4:20-21). This is a message for us when we have unbelief, do not focus on the unbelief but press on and be strengthened in faith. Paul writes;
"Brothers, I do not consider to have made it my own, but one thing I do; forgetting that behind and reaching out to that ahead, I press on toward the goal of the prize of the upward call of God in Christ Jesus" --Philippians 3:13-14Faith is a belief in things unseen, of God’s existence, and also works to persuade us of God's promises so that we live according to His will. Faith and love roots us and establishes us in Christ.* Peter writes the goal of faith is the salvation of the soul (1 Peter 1:9). We are born of the Spirit which makes our spirit alive and also works with the truth to regenerate us, so we have this testimony from God.
If we are to walk by the Spirit and walk by faith, these would seem to be mutually agreeable. Jesus said his word exists Spirit and Truth. The Spirit guides us into truth, to abide in his words, thus we can discern between a spirit of error (often seen as pride) and Spirit of truth. Jesus emphasized the importance of faith, teaching His disciples that even a small amount of faith could accomplish great things (Matthew 17:20).