Paul's fifth argument against the Judaizers is that the law, misunderstood as a way of salvation, only brings a curse (Galatians 3:10–14). Paul cites four Old Testament passages, proving once again that the Judaizers are not being faithful to the teaching of the old covenant, as they claimed.
First, Paul quotes Deuteronomy 27:26: "Cursed is everyone who does not continue to do everything written in the Book of the Law." It is clear that nobody obeys the law perfectly, so everybody falls under the curse of the law. According to Genesis 2 and 3, the curse is death. Thus, the law cannot possibly give life and salvation to men; it can only work death. Those under the curse of the law can only find life by trusting in the promises, apart from the law.
Second, Paul quotes Habakkuk 2:4: "The righteous will live by faith." Life, says Paul, comes by means of faith, not by means of earning favor through works. Day by day the righteous man finds life by believing the promises, and then after receiving life, he lives a life of obedience to the law.
Third, Paul quotes Leviticus 18:5: "The man who does these things will live by them." God was telling the people that if they lived faithfully, trusting and obeying, they would grow in life and sanctification. In context, Leviticus 18:5 presupposes faith, and simply means that true faith—the kind that gives life and growth in salvation—is obedient faith. It seems, though, that the Judaizers were misusing Leviticus 18:5 to teach that law-keeping by itself produces salvation. Paul pits their misreading of Leviticus 18:5 against the clear statement of Habakkuk 2:4 and argues that if we separate the law from faith, and use the law as a means of getting salvation, all we shall find is the curse and death.
Finally, Paul quotes Deuteronomy 21:23: "Cursed is everyone who is hanged on a tree." Jesus was hanged on a tree, and took the curse of the law on our behalf. This is what delivers us from the curse of the law, and enables us to find true life when we put our faith in Christ's atoning work, on His life, and His cursed death.
The curse to which Paul refers is nothing less than exposure to the unmitigated wrath of God Almighty. It is a frightful and dreadful thought, eclipsed only by the reality that this is the destiny of all those who do not live by faith in Christ. Ask God to move your heart to greater compassion and evangelistic outreach to the lost.