What does Galatians 3:18 mean?

Paul continues to make the case that salvation does not come through following the works of the law of Moses. Specifically, the eternal blessings God promised to Abraham and his offspring are not given on the basis of deeds or actions. Instead, it comes to all who believe by faith in Christ. Christ is the ultimate offspring of Abraham, and He is entitled to everything God promised to Abraham. So everyone who is "in Christ" is also entitled to those promises through Him (Galatians 3:10–14).

Now Paul makes an undeniable point of logic. He describes the covenant promises made to Abraham as an "inheritance," something passed down from one person to his or her offspring. This inheritance was given by God's promise. Theologians call it a "unilateral covenant," meaning that it was one-sided. God didn't ask Abraham to do anything to receive His promises. Abraham already believed God; God promised Abraham specific blessings with no strings attached. If you have to now follow the law of Moses to receive the blessings God promised to Abraham, what kind of promise is that? In short, it turns unconditional blessings into conditional ones. It changes God's gift from a promise to a merit-based performance, one we can never be good enough to merit (Galatians 3:10; Romans 3:10).

This raises an obvious question, one the Judaizers must have asked loudly and sarcastically: So what was the point of the law, then? Paul will answer that in the following verses.