Paul presents five arguments to show that source of justification is faith in Jesus Christ and not the deeds required by the law of the Old Testament.
To be a Jew is of a great value:
But if that is the case, why then the Jewish apostles and disciples - Peter, Paul, Barnabas and many others - accepted the Gospel of Jesus Christ? By this acceptance alone, the Jewish Christians confess and proclaim that the law does not save.
Why then do the Galatians want to accept the law? It is simple foolish. The pillars of the Church in Jerusalem and many other Jewish Christians confess that the Law cannot save, and here are the Galatians, who by going to the Law confess that Jesus is not sufficient for their salvation.
In the Hebrew Bible we read: “Do not enter into judgment with Your servant, for before You no creature is in the right” (Ps 143:2).
In the Septuagint, we read: “And do not enter into judgement with Your slave, because no one living will be counted righteous before you” (Ps 143:2 LXX).
Paul takes the message of the psalm and applies it to the law saying: “for by the works of the law no flesh will be justified” (2:16b). Paul draws conclusion from the Psalm in the Septuagint version. If no one living will be counted righteous before God, that also includes the Jews, who already possess the law. That means the law has no power to justify anyone. Again, why do the Galatians want to accept the law then?
If you still look for the law that means that Christ is not enough for you. In this way, you confess your lack of faith in the redeeming power of Christ’s death on the cross. In this way, you proclaim that you still remain in sins.
At the beginning of the letter, Paul stated that Christ willingly gave up himself for our sins (1:4). The Galatians by going to the Law proclaim that their faith in Christ was not enough to justify them from their sins. In this case, it would mean that Christ failed.
Yet, there can be another problem, namely if one removes the law what does prevent him/her from sinning? Imagine a Christina, who takes his/her freedom from the law as a license to sin. In that case, they would portray Jesus as “the minister of sin”.
The Pharisees in the Gospel complained that Jesus associated himself with sinners (Mark 2:16). Why? To let them go on sinning?Why does a doctor associate himself with the sick? To let them remain sick? (See Mark 2:17). Jesus die on the Cross for our sins (Gal 1:4), so we could be free from the power of sin. That is the meaning of justification. If that is so, why do you need the law then?
V. 18 - Imagine a Jew, who has the law, then abandon the law for Christ - like Paul - and then goes back to the law. What does it say? That he had made a mistake by leaving the law, that he had “sinned” by abandoning the law, that Christ is not enough (see Acts 21:21, Rom 10:4).
V. 19 - “For I through the law to law died in order that I might live to God”. Perhaps, Paul means that his attempt to fulfill the law proved futile. In Philippians 3:6, he claims to be blameless according to the righteousness of the law. Yet, he realized that such righteousness was turning him into a violent man, willing to destroy the lives of others (Acts 26:10–11). Then, he gave up on the law and embraced Christ. Since then, he was a new man.
The word “die to somebody or something” means to remove oneself from the influence of this person or thing. Paul presents a clear contrast. The one who lives for the law is unable to live for God. Only by removing oneself from the influence of the law, one can live for God.
“With Christ I have been co-crucified”. It is a clear reference to the sacrament of baptism (Rom 6:1–11).
V.20 - Paul’s spiritual death to the law has become the beginning of his new life as an apostle/slave of Christ, a new man who brings others from darkness to light (see Acts 26:18). Yet, it is actually not him who lives. The old Saul died at Damascus (see the significance of three days without eating and drinking, and seeing in Acts 9:9). This old Saul would never come back to life. So although Saul continue living and has even change his name into Paul, but actually it is Christ, who was born and lives in him.
So what is the meaning of Paul’s life? Before Damascus it was the law, zeal for the tradition of his ancestors, and persecution of the Church. Now? It is faith in Jesus Christ loved him to the point of the Cross.
The last argument draws the final point from all the other arguments. Salvation in Christ, justification by faith is God’s grace. On the other hand, justification by the law, the righteousness of the law that Paul was so proud of, is not. The righteousness of the law is the fruit of our own effort. These two cannot be combined. Thus, if one accept the Law - like the Galatians planned to do - then one rejects God’s grace and declares that Christ died in vain.