5Does he who supplies the Spirit to you and works miracles among you do so by works of the law, or by hearing with faith— 6just as Abraham “believed God, and it was counted to him as righteousness”? 7Know then that it is those of faith who are the sons of Abraham. 8And 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.” 9So then, those who are of faith are blessed along with Abraham, the man of faith.
To get the people to see how law keeping has nothing to do with getting saved, Paul appeals to the greatest patriarch of them all – Abraham. If anyone is going to be justified on the basis of works/law, it is Abraham.
Paul takes it for granted that the Galatians know that Abraham was justified by faith and not works. “You know that Abraham was justified by faith. Why then would you think that you are not?” is his argument. This is very similar to Jesus’ statement to Nicodemus when Nicodemus expressed amazement at Jesus saying he must be born again. “How is it”, Jesus said to him, “that you are a teacher of Israel and do not know these things?” (John 3:9-10).
Similarly, when Jesus is walking with the two disciples on the road to Emmaus after His resurrection he expresses surprise that His death and resurrection should come as a surprise to them (Luke 24:25-27). In other words, the Old Testament has enough in it to direct to Christ and when Christ came, believing Jews should have seen Him as the Messiah.
The concept of new birth is not new in the New Testament. It is developed and explained more clearly and we see Jesus as the fulfillment of what the Old Testament teaches.
Justification by faith plus nothing is not a new concept. It is expressly said about Abraham. The Gospel of Jesus Christ is found in the Old Testament. The New Testament sheds light and gives all the details about it, but Jesus expected Nicodemus and the disciples in Luke 24 to know about it even before the New Testament was written, even before the new covenant was introduced. Paul will use the example of Abraham again in a more developed and powerful manner in Romans 4.
Make a commitment to read and understand the Old Testament better than you do. The theme of the whole Bible is salvation through faith in Jesus Christ. Check Old Testament references that are used in the New Testament. Look for the Gospel in the Old Testament. The whole Bible is one story of God rescuing sinners from judgement. Be sure to read the Book with the purpose and plot line in mind. You’ll miss what the Bible is all about if all you do is see it as a bunch of stories that are largely disconnected.
Embark on the great adventure today of understanding the whole story that God has given us to tell us how He is going to save the world.