Therefore, be sure that it is those who are of faith who are sons of Abraham.Galatians 3:7(NASB)
Just as Abraham was justified because he believed what God had said, so we too are declared righteous by faith in Jesus Christ our Lord. God's dealings with Abraham had nothing to do with what Abraham did but rested entirely on that fact that he believed the Word of God.
And God's dealings with the Galatian Christians is no different from God's dealings with the believers of today - our righteousness has nothing to do with what we do but rests entirely on believing in Christ and what He did. All that we are in Christ and all that we have in Him is not based on our merit. It does not rest on our good deeds or works of the law - our salvation rests on Christ and is ours by faith in the truth of God's Word.
Abraham was declared righteous by faith and we also are justified in the same way - by the hearing of faith - by believing God's Word - by trusting all that He has written for our learning. And Paul argued that being justified has nothing to do with being a physical descendent of Abraham. It has nothing to do with being circumcised or being able to trace your genealogy back to the patriarchs. Being a son of Abraham is a matter of faith - both in the Old and New Testaments.
Justification is an act of God in the life of a man or woman who believes in Him and trusts His Word. The only reason God is able to deal with sinners in this way is because the Lord Jesus paid the penalty price for our sin. Abraham believed God when He called him out of his home town to a place that God had promised as an eternal inheritance and Abraham obeyed by faith - and his faith was credited to him as righteousness. Noah believed God and built an ark, by faith. Nehemiah believed God and built a wall. David, Daniel, Isaiah, and the many saints listed in Hebrews believed the Word of the Lord - and they were justified by their faith.
We have greater revelation than Abraham, Noah, David, and others in the Old Testament, for we have the whole council of God. We are not called by God to believe God by leaving our home and going to a certain place by His direction like Abraham. In this Church age, we are called to believe on the Lord Jesus Christ for the forgiveness of sins and life everlasting. When we believe this by faith... just as Abraham believed God by faith, it is credited to us as righteousness and we are declared justified in the eyes of God. Jesus said, "THIS is eternal life, that you believe on GOD and on HIM Whom He has sent."
Israel may have been the physical descendants of Abraham and even chosen to be entrusted with the Law, the prophets, and the promised Messiah, but they were saved by faith in the Word of God, not simply because they were physical descendants of Abraham. In this Church dispensation, it is those who believe by faith who are reckoned by God as the spiritual descendants of Abraham. Believing Jews and believing Gentiles alike are the spiritual offspring of Abraham - we are justified by faith. In this dispensation of the age of grace, those that do not trust in the only begotten Son of God, whether Jew or Gentile, are not considered by God as the spiritual seed of Abraham. They are not children of God and they are not justified in the sight of God.
The whole book of Galatians deals with this serious problem... that we are not justified by the works of the Law, by physical heritage, or an accident of birth. We are justified by faith. However, certain Jewish teachers were unable to let go of their insular religion in the Church in Galatia and Paul gave a strong and severe warning - that the sons of Abraham are those of faith. He reminded them of a verse from Habakkuk: "The just shall live by faith," and that Scripture itself foretold that God would also justify the Gentiles by faith in the same way that He justified the Jews by faith - for the Lord told Abraham: "In you shall all the families of the earth be blessed."
God has not finished with Israel, and during the coming 70th week of Daniel He will once again work through that special nation. They will go into all the world and preach the gospel of the Kingdom to everyone. But in this dispensation of the grace of God, all believers, Jew and Gentile alike, are children of faith and members of the Body of Christ. We are all one in Him and have been commissioned to be ministers of reconciliation who share the good news that Christ died for our sin, was buried, and rose again the third day - and all who believe on Him will not perish but have everlasting life - and it is all by faith.
Heavenly Father, thank You that I have been justified by faith and that by faith, I am considered to be a spiritual seed of Abraham. Thank You that through faith, I have peace with God and the peace of God in my heart. In Jesus' name, AMEN.