“Sing, O barren one, who did not bear; break forth into singing and cry aloud, you who have not been in labor! For the children of the desolate one will be more than the children of her who is married,” says the LORD. Isaiah 54.1

In the whole book of Galatians, Paul is trying to distinguish two, contrary ideas in the minds of the Christians to whom he is writing: flesh and promise. The word “flesh” is synonymous with slavery, and “promise” is synonymous with liberty. This is the allegory that Paul makes mention of in verses 21-31 of chapter four.

Before we get into the thick weeds of this passage, it should be noted that Paul here announces that he—as a divinely-inspired, apostle of Jesus Christ — is going to allegorize the story to which he refers. When the Bible announces that it is allegorizing, then it’s clearly allegorizing. We can abuse the scriptures when we over-allegorize parts of the Old Testament. This should caution us to a careful understanding and handling of Scripture, lest we speak confidently and creatively where the Bible does not speak.

Paul uses the story of Abraham’s offspring to communicate his point against the Galatian Judaizers’ understanding of the law of God. According to their ideology, gentile Christians must first become Jews (by way of circumcision) in order to become true children of God. To put it in other terms, they believed that the children of God by promise must first become children of God by the flesh, so that they can be true children of God. Paul vehemently disagrees.

Paul tells the Galatians that there were two sons born to Abraham: Ishmael and Isaac. The son born of the flesh is Ishmael, since he was born of Hagar, through the planning of Abraham and Sarah, not the promise of God. But Isaac was born of God’s promise by the coming together of Abraham and Sarah. So, why is it that Ishmael was not valued the way that Isaac was? After all, according to Hebrew culture in that day, the first-born son should have been the heir of the promise.

The only claim that Ishmael had to the inheritance of Abraham was through the flesh. Through the allegorizing of this story, Paul is demonstrating the superiority of the spiritual realities of God’s promises to mere fleshy realities. The very last time that flesh was valued as worthy of anything in the economy of God was when Jesus Christ paid in full the ransom for all of God’s elect as he died on the cross. Paul highlights this point by quoting Isaiah 54.1, where Isaiah says that it is the barren one who can rejoice, the desolate one who will have more children than the woman who is married. Isaiah goes on and on to describe the blessings of God to all of those under the new covenant, and none of these blessings come to the people of God because of their fleshy fulfillment of the law. Rather, blessings come to the children of God by the promises of the Lord who has compassion.

Paul closes this section with a reminder to the Galatians that they are not children of slavery, but children of promise. Just like with Ishmael and Isaac, the child of slavery is picking at the child of the promise. What Paul means is that the Judaizers are messing with the Galatian Christians by trying to enforce a law of circumcision, of the flesh. Paul encourages the Galatians by reminding them that, just like with Ishmael, the Judaizers will be cast out, unable to inherit with the children of promise.

See, the great irony is that by adding fleshy fulfillment of the law to the promises of God, the Judaizers miss the promises of God and demonstrate their unbelief. If we add even the slightest bit of our accomplishments to the death of Jesus Christ on our behalf, we hinder the power of the gospel to wholly transform us into Christ’s image, because we demonstrate our unbelief. Salvation is all of grace, and we muddy the waters when we try to work to fix ourselves.

The promise of God is salvation to all who would believe in the death, burial, and resurrection of God’s perfect Son, Jesus Christ. No act of ours, in our flesh, could ever add anything to that.