Problem: This passage is difficult to understand, because it is so tightly woven into the OT. Is Paul handling the OT properly?
Solution: The Judaizers (false-teachers) in Galatia were telling the believers that they needed to go back under Law, if they wanted to be blessed by God. In this section, Paul is arguing against this teaching. To argue his case, Paul argues from the OT.
First, Paul uses the words “blessing” and “cursing” because he is drawing from Deuteronomy 28. In the OT, the Jews were given either a blessing or a cursing for their fulfillment and obedience to the Law (Deut. 28). The Law of Moses was not an unconditional covenant; it was a conditional covenant. God’s blessing was contingent on their obedience. The Judaizers were arguing that God’s blessing is connected to the Law, because God’s will is immovable. If he said that his blessing is contingent on Law (Deut. 28), then this wouldn’t change –even after Christ. At least, this is the way the Judaizers probably argued their case. However, Paul lifts this teaching of “blessing” and “cursing,” and he places its fulfillment onto Christ.
Second, Paul argues that the cursing and blessing was fulfilled in Christ on the Cross, who was the Curse-Bearer. The Jewish believers in Galatia were most likely troubled at the blessing and cursing of the Law. The false teachers capitalized on this fear, and they explained that believers in Jesus needed to come under the Law in order to remain in God’s blessing. In response, Paul argues that God’s curse was placed on the Curse-Bearer: Jesus. Paul writes that the Curse-Bearer died in the sight of all “publicly portrayed as crucified” (Gal. 3:1). The death of Christ was not a secret. Paul argues that it was a public display of God.
Next, Paul cites Deuteronomy 21:23 to support the fact that Jesus took the curse of the law in his mortal body. Paul writes, “Christ redeemed us from the curse of the Law, having become a curse for us–for it is written, ‘CURSED IS EVERYONE WHO HANGS ON A TREE’” (Gal. 3:13). It must have been difficult for an OT Jew to see the Messiah hanging from a tree, because the Messiah was supposed to be blessed by God (not cursed). If the Messiah was hanging from a tree, then this meant that the Messiah was cursed by Yahweh. Paul cites this verse to support the fact that this was exactly the case! Jesus was cursed on the Cross, as the Law dictates, and he took our curse for us. Paul’s interlocutor might ask, “Doesn’t someone have to be cursed for failing to uphold the Law?” Absolutely! –writes Paul. Jesus took the curse for us. Therefore, the Law was fulfilled through Jesus’ work as the Curse-Bearer, and we are no longer under the Law, because he fulfilled the curse of disobedience to Law.
Third, if we want to go back under Law, Paul argues that we need to keep the entire Law. Paul is arguing, “You can have the ultimate and perfect blessing of God through Jesus. And, if you go back to the Law, you will only get cursing. Why on Earth would you ever want to go back under Law?!” Paul argues that going back under the Law will only bring a curse.
Fourth, Paul argues that God planned to bring blessing through faith (not Law) from the very beginning of the Bible. To support this argument, Paul cites Abraham (Gen. 15:6). The Judaizers were explaining that Moses’ Law can bring God’s blessing, but Paul cites Abraham, who existed 500 years before the Law was given. In fact, God’s plan was to bring Abraham’s blessing (not Moses’ blessing) to “all the nations” on Earth. In other words, God never planned to bring the Law to the Gentiles; he planned to bring blessing (apart from Law) to the Gentiles (Gen. 12:3; 18:18; 22:18). This is why Paul writes, “The Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, “ALL THE NATIONS WILL BE BLESSED IN YOU.”” (3:8). This would have been a striking theological point for Paul’s adversaries, who were promoting circumcision and Law! The Law wasn’t promised to spread to all people on Earth, but the blessing through faith was promised to spread to all people on Earth.
Fifth, Paul quotes Habakkuk 2:4 to support his case. In the book of Habakkuk, Israel is being judged by the Gentile nations, because they didn’t keep the Law. Therefore, because they didn’t obey the Law, they went under the curse of God. Habakkuk told his people that the way out from under the curse of God (i.e. takeover by the Gentile nations) was by faith. Nothing has changed in this regard. Paul argues that God would bring people out from under the curse because of faith (during Habakkuk’s time), and he will bring NT believers out from the curse by faith (during our time).
In conclusion, Paul’s argument is strong. He shows that the plan of God was originally by grace (Gal. 3:18) through faith (Gen. 15:6) apart from works (Gal. 3:12-13) and for all people (Gen. 22:18). This all occurred before the Law was given.
 In the Septuagint, the Greek word for “blessing” is eulogeo, and the Greek word for “cursing” is katara. Both of these words are used, for example, in Deuteronomy 30:19. After he gives the people the Law, Moses tells the people, “I call heaven and earth to witness against you today, that I have set before you life and death, the blessing (Greek eulogeo) and the curse (Greek katara)…” (LXX) Thus, the blessing and cursing of God is dispensed by the keeping of the Law. Paul’s enemies in Galatia would have known of this concept.
 Stott writes, “This verb prographein means to ‘show forth or portray publicly, proclaim or placard in public.’ It was used of edicts, laws and public notices, which were put up in some public place to be read, and also of pictures and portraits.” Stott, John R. W. The Message of the Galatians: John R.W. Stott. Leicester, England: Inter-Varsity, 1986. 74.
And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed. So then they which be of faith are blessed with faithful Abraham. For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them. But that no man is justified by the law in the sight of God, it is evident: for, The just shall live by faith. And the law is not of faith: but, The man that doeth them shall live in them. Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree: That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.