Galatians 4:21 - Meaning and Application

In these verses, Paul shows the difference between believers who rest in Christ and the Judaizers who trust in the law by using the story of Isaac and Ishmael. He introduces it in a way meant to arrest their attention and make them feel how wrong it is to turn from the truth and lose the freedom of the gospel. “Tell me,” he says, “you who want to be under the law, do you not hear the law?” He assumes they do hear it, because it was read in Jewish gatherings every Sabbath. Since they were so eager to be under it, he wants them to think carefully about what it actually says, especially in Genesis 16 and 21.

First, he lays out the story itself (Galatians 4:22, Galatians 4:23). Abraham had two sons. One, Ishmael, was born to a slave woman, Hagar. The other, Isaac, was born to a free woman, Sarah. Ishmael was born in the ordinary way, by the natural course of things. Isaac was born by promise, when there was no natural reason to expect Sarah to have a son.

Then Paul explains the meaning of the story, or the use he wants to make of it (Galatians 4:24-27). These things, he says, are an allegory, meaning they point beyond the literal story to a spiritual truth. God may have intended Hagar and Sarah to stand for the two covenants, or two different ways God dealt with his people. Hagar represents the covenant given at Mount Sinai, which produces bondage. It was a gracious covenant, but compared with the gospel, it was a covenant of slavery. It became even more like bondage for the Jews because they misunderstood it and expected to be made right with God by keeping its works.

Paul says this Hagar stands for Mount Sinai in Arabia, since the Arabs called that mountain Hagar. It also matches “Jerusalem that now is,” meaning the present Jewish system, which was still in bondage along with its children. Sarah, on the other hand, points to “Jerusalem above,” the state of Christians under the new and better covenant. That covenant is free from the curse of the moral law and from the burden of the ceremonial law. It is the mother of us all, because all, Jews and Gentiles alike, are welcomed into it through faith in Christ. Paul also points to Isaiah 54:1, where the prophet speaks of the barren woman rejoicing, because the one who seemed desolate would have more children than the one who had a husband.

Paul then applies the story to the believers he is writing to (Galatians 4:28). “Now we, brothers,” he says, “like Isaac, are children of promise.” Christians who receive Christ and rely on him alone for justification, that is, being made right with God, and salvation, are counted as Abraham’s spiritual children, even if they are not his natural descendants. Because of that, they also share in the promised inheritance and its blessings.

Paul knows they may be troubled by the Jews, who were strongly attached to the law and ready to persecute those who would not submit to it. He tells them this opposition was already shown in the type, because the one born according to the flesh persecuted the one born according to the Spirit. They should expect the same pattern now. But he also gives them comfort from Scripture, quoting Genesis 21:10: “Cast out the slave woman and her son, for the son of the slave woman will not share the inheritance with the son of the free woman.” Even if the Judaizers hated and opposed them, the end would be that Judaism would fade and perish, while true Christianity would keep growing and remain forever.

So Paul closes with a simple conclusion (Galatians 4:31): “We are not children of the slave woman, but of the free woman.”