What is a summary of the book of Galatians?

from the old testament

• The book of Galatians is not in the Old Testament.

from the new testament

• The letter to Galatia is written against the backdrop of Jewish influencers, known as “Judaizers” (Galatians 2:4), who were trying to bring Law obedience into Christianity. They were not necessarily denying the importance of Christ's death, but by adding the Law, they were undermining the gospel.
• This error was not exclusive to the Galatian region. Acts 15 records the first church council convening because “some men came down from Judea and were teaching the brothers, ‘Unless you are circumcised according to the custom of Moses, you cannot be saved’” (Acts 15:1).
• Because Paul attended that council (Acts 15:2), scholars are divided on whether it directly influenced Paul’s letter to the Galatians. Those who connect it say that Paul wrote to them as a result of the council, writing to Northern Galatia (the outer regions of Galatia), where the Gospel had reached by that time. Others believe that the connection is forced and instead think Paul wrote to Southern Galatia (actual Galatia) before the council. They view this letter as reflecting the growing need for such a council. Though how one understands the letter’s connection to the council affects its nuances, the letter’s meaning remains unchanged.
• Unlike other letters where Paul spends some time giving thanks for the church (e.g., 1 Corinthians 1:4), Paul quickly jumps into an attack on the error besieging the Galatian church. He opens with a confrontation: “I am astonished that you are so quickly deserting him who called you in the grace of Christ and are turning to a different gospel” (Galatians 1:6). By “different gospel,” the rest of the letter explains that the Judaizers were saying the believers needed to be circumcised (Galatians 5:2–3), adding works of the Law onto faith in Jesus. Paul countered that, “Even if an angel from heaven or we should preach to you a gospel contrary to the one we preached to you, let him be accursed. As we have said before, so now I say again: If anyone is preaching to you a gospel contrary to the one you received, let him be accursed (Galatians 1:8–9).
• However, Paul was aware that the enemies were saying that they had the correct Gospel, so Paul spent considerable time reminding them that He had been called by God and received the Gospel directly from Him (Galatians 1:11–24) and that the other apostles tested him and found his Gospel accurate (Galatians 2:1–6). Indeed, they were so confident that just as Peter had been sent to the Jews, the apostles sent Paul to the Gentiles (Galatians 2:7–10).
• Adding to his confidence in the true gospel, he also recounted a time when he confronted Peter, who had started to be drawn toward separating from the Gentiles and associating exclusively with the Jews (Galatians 2:11–14). He gave the thrust of his corrective to Peter as “We ourselves are Jews by birth and not Gentile sinners; yet we know that a person is not justified by works of the law but through faith in Jesus Christ, so we also have believed in Christ Jesus, in order to be justified by faith in Christ and not by works of the law, because by works of the law no one will be justified” (Galatians 2:15–16). Peter knew better—the Law doesn’t save. But he was still tempted to treat Jews as superior to Gentiles, behaving in a way contrary to the Gospel. Paul reminded him that both Jews and Gentiles are saved only through Christ and not by works.
• Turning to his readers, Paul then brought the same argument against them. Calling them “O foolish Galatians!” he reminded them of the Gospel they had heard and believed (Galatians 3:1), rhetorically asking whether they received “the Spirit by works of the law or by hearing with faith?” (v 2). The implied answer is: if they received salvation by the Spirit, why do they now think they can be perfected by their works (v 3)? As Paul does elsewhere (cf. Romans 4), he reminds them that Abraham came before the Law and was justified by faith (Galatians 3:6) and thus only those who believe by faith are like Abraham (v 7).
• In contrast, “all who rely on works of the law are under a curse; for it is written, “Cursed be everyone who does not abide by all things written in the Book of the Law, and do them” (Galatians 3:10). While the Judaizers were primarily promoting circumcision, by adding one Law to the Christians they were placing the Galatians under the obligation to obey the entire Law, causing them to be severed from salvation in Christ (Galatians 5:4). But, because no one can obey the Law, “it is evident that no one is justified before God by the law” but, instead, “The righteous shall live by faith” (Galatians 3:11).
• Paul then explained why the Law even existed if not to save people. It was God’s means of showing people they couldn’t be saved and that they needed a Savior (Galatians 3:19–29).  He called it a “guardian until Christ came, in order that we might be justified by faith.”
• Paul then encouraged the true believers in Galatia, reminding them that faith in Jesus meant they were sons and daughters of God (Galatians 4:6–7) and no longer slaves to sin. Because of this, they were no longer under the Law but free from it (Galatians 5:1).
• However, anticipating an error in the other direction, Paul explained that though they were free from the Law, that was not a license to sin. Rather, “walk by the Spirit, and you will not gratify the desires of the flesh. For the desires of the flesh are against the Spirit, and the desires of the Spirit are against the flesh” (Galatians 5:16–17). Having the Holy Spirit meant that obedience was expected. But that obedience didn’t justify. Rather, it proved that the Holy Spirit was living in them, producing fruit of righteousness in their lives (Galatians 5:22–23).
• Because believers are not to continue in sin, Paul ended by encouraging them to watch out for one another (Galatians 6:1–5) and to do good (Galatians 6:6–10). He ends by summarizing the letter: “It is those who want to make a good showing in the flesh who would force you to be circumcised … For even those who are circumcised do not themselves keep the law, but they desire to have you circumcised that they may boast in your flesh. But far be it from me to boast except in the cross of our Lord Jesus Christ, by which the world has been crucified to me, and I to the world. For neither circumcision counts for anything, nor uncircumcision, but a new creation” (Galatians 6:12–15).

implications for today

The gospel is not a message to be tampered with. It alone saves. This is why Paul was so hard in the letter to the Galatians. They were being seduced into obeying the Mosaic Law in addition to believing in Jesus to be saved. Yet adding requirements to salvation beyond faith alone is to preach another gospel.

What is the pure gospel? We are all sinners (Romans 3:23) and unable to save ourselves from God’s justice (Romans 3:19–20). The gospel, meaning “good news,” is the message that God sent His Son to die in the place of sinners, so that all who believe in Him will be saved (John 3:16).

Today, the purity of the gospel continues to be challenged. Some groups that consider themselves Christian require specific works to be saved or to continue in salvation. Examples include attending Mass, taking communion, being baptized, or even belonging to a specific denomination. But none of these are the gospel that Paul preached. Were he alive today, he might say as he did to the Galatians, “If anyone is preaching to you a gospel contrary to the one you received, let him be accursed” (Galatians 1:9).

However, there’s another error Paul addressed: treating obedience as unnecessary. A believer is not saved, nor kept saved, by works. However, because the Holy Spirit lives in us (Romans 8:9), we are expected to bear the fruit of the Spirit (Galatians 5:22–23), crucify our flesh (Galatians 5:24), and walk in the Spirit (Galatians 5:25). Therefore, even as we avoid the one error of making works the requirement for salvation, we must avoid the other of not obeying Jesus (John 14:15)!