We now arrive in our series at one of the most intricate yet deeply enriching sections of the epistle. Here Paul paints a vivid and dramatic contrast between the law and the gospel, setting before us a theological picture that is both complex and profoundly illuminating. In this passage, we are given a full apologetic for the argument Paul has been developing from the very beginning. He defends the true gospel by appealing directly to the Old Testament Scriptures, demonstrating that the Judaizers were not only proclaiming a message contrary to the gospel of Christ, but one that stood in opposition to the very testimony of the Old Testament law itself.
Paul will draw a sharp line between the law and the promise, associating the law with natural descent—life “according to the flesh”—and the promise with spiritual descent—life born through faith. He frames this contrast through a rich tapestry of imagery: two mothers, two sons, two mountains, two covenants, and two Jerusalems. Each element reinforces the central truth that the inheritance of God does not come through human effort or lineage, but through the gracious promise fulfilled in Christ.
This section is demanding, but its reward is great. Paul’s inspired argument not only clarifies the relationship between law and gospel but also anchors the believer’s confidence firmly in the promise of God, not in the works of the flesh.
The Text
Tell me, you who want to be under law, do you not listen to the law? For it is written that Abraham had two sons, one by the bondwoman and one by the free woman. But the son by the bondwoman was born according to the flesh, and the son by the free woman through the promise. This is allegorically speaking, for these women are two covenants: one proceeding from Mount Sinai bearing children who are to be slaves; she is Hagar. Now this Hagar is Mount Sinai in Arabia and corresponds to the present Jerusalem, for she is in slavery with her children. But the Jerusalem above is free; she is our mother. For it is written,
“Rejoice, barren woman who does not bear;
Break forth and shout, you who are not in labor;
For more numerous are the children of the desolate
Than of the one who has a husband.”And you brethren, like Isaac, are children of promise. But as at that time he who was born according to the flesh persecuted him who was born according to the Spirit, so it is now also. But what does the Scripture say?
“Cast out the bondwoman and her son,
For the son of the bondwoman shall not be an heir with the son of the free woman.”So then, brethren, we are not children of a bondwoman, but of the free woman. (Galatians 4:21-31)
The Question of Law
Paul begins this section in v.21 by asking a question to the recipients in respects to their obedience to the law. If they want to be under the law, why aren’t they listening to it? In 3:24-25 and 4:2-3, Paul compared circumcision and obedience to the law as being under the law or a tutor. To place yourself under the covenant stipulations of Sinai was to place yourself under the law and in return, the scriptures tell us it was to become a slave. In contrast, to be under the covenant of grace is to be an heir and an heir according to the promises to Abraham. But Paul’s question is meant to clarify the idea of being under this law. He asks: do you not listen to or hear the law? It is a listening that demands obedience to the stipulations of that law whether in the Pentateuch or in the whole of the Old Testament Canon. The question itself answers the question. They wanted to be circumcised into the Old Covenant but they weren’t listening to the law. Why?
Two Sons of Abraham
In v.22, Paul begins with the term “for” denoting an explanation of something. Why have they not listened to the law? Because it is written that Abraham had two sons, one a slave and one free. If they had listened to the law, they’d have known this. Abraham was the key to which the blessing of God would be granted but not all his descendants would be on equal par and in return not all would receive the blessing. The sons of Abraham came from two different mothers. Paul describes one as a freewoman while the other a slave woman. While he doesn’t name them, he ascribes characteristics that lead us to conclude that the bondwoman is Hagar (Genesis 16:15) while the freewoman is Sarah (Genesis 21:2). So, one of the two children of Abraham was born a slave while the other was born a free man. They should know all about this since they were placing themselves under the stipulations of the law which included this story in Genesis.
The Two Births
Now, in v.23, Paul approaches the difference between the two sons on another front. One was born of the flesh (law – slavery) while the other was born according to the promise (spirit – freedom). This was to contrast them further. They were not alike! You can’t mingle grace and law since it would be equivalent to mixing slavery and freedom. You are either a slave or you are free! You receive the blessing by earning it or by promise. But what exactly is this contrast between these two terms and how does it relate to their births? The birth of Ishmael was achieved because of the efforts of Sarah in giving Hagar to her husband to produce Ishmael. They took it upon themselves and their own works to try to fulfill a promise of God. On the other hand, with Isaac, Sarah was old and barren, but because God had promised her a child who would be the heir of Abraham, He fulfilled it despite them. What we don’t want to miss in this verse is that while both were circumcised according to the flesh, still, only one would be the channel of the promises which eventually would lead to Jesus as the sole heir (Galatians 3:16)[1].
Two Covenants, Two Mountains & Two Jerusalems
In v.24, Paul now takes the two sons from the two women comparison and is going to provide an application or an allegorical about these things to them to teach them about how foolish it is to place themselves under the law. He is using this example to speak upon a set of realities that is present in their day (and in ours). Fundamentally, when reading this narrative, we see however that his main thrust is a typological interpretation of these things.
He compares these two women to two covenants. The first covenant is probably the Sinaitic Covenant while the other the New Covenant or perhaps the Abrahamic Covenant of faith. One he identifies with Mount Sinai but the other he doesn’t identify at all. Not only is Hagar compared to Mount Sinai, but she is also compared to the old Jerusalem. The first thing we should note is that the location mountain is explicitly mentioned. This is the place where the Hebrews received the law and now it is allegorically compared to the current Jerusalem. The agitators were boasting that they had authority because they were from Jerusalem where Jesus had begun His ministry and where the faith was initiated. They were using this to their advantage and may have carried weight with the Galatians. Paul defines this current Jerusalem as a place of slavery (to sin), and in return, it could only produce slaves. So, in essence, being from Jerusalem meant absolutely nothing since those who promulgate a false gospel are doing so with the intent to enslave believers to the law because it continues to place itself under the Sinaitic covenant.
The Free Jerusalem
In comparing the old Jerusalem to Hagar, Paul now turns to the New Jerusalem or the Jerusalem from above in v.26, who he refers to as their mother. This is a heavenly Jerusalem that he is referring to here. The New Jerusalem is a prominent theme in the latter chapters of Hebrews. This was the city that Abraham was looking for, whose architect and builder is God (Hebrews 11:10). It is compared to a desired country, a heavenly one (Hebrews 11:16). Hebrews compared this heavenly Jerusalem to Mount Zion, the city of the living God (Hebrews 12:22; Revelation 3:12; 21:2). The old Jerusalem, with its covenant and its law, is no longer the path God calls His people to follow, because the New Jerusalem and the New Covenant have revealed the fullness of His plan through Christ and the Spirit. The Galatians had been born again by the Spirit and were now free from the law’s covenantal demands.
For my Dispensationalist brothers, this presents a real difficulty. If one anticipates a future return to Old Testament laws—circumcision, rituals, animal sacrifices for sin, and festivals—these practices are often viewed as positive or spiritually enriching. Yet Paul insists that returning to the covenant of law is not a step forward but a step back into slavery and under the curse that the law brings.
The Barren Woman
To substantiate this allegory, Paul now turns to a proof text in Isaiah 54:1. The text in Isaiah is referring to a time when Jerusalem would be in exile and then return. But what does this have to do with Sara & Hagar, two Jerusalems and two sons? Personifying a city as a woman is not unique (See Psalm 87:5; Lamentations 1:1-7)
In this context, Paul is comparing the barren woman to Sarah. While she was barren, her condition would change because of the promise of God. She would have more children than the one with the husband (Hagar), children as numerous as the star in the heavens (Genesis 15:5). Isaiah is looking ahead to an Israel that would be reborn and no longer be under a curse (Isaiah 64:10). Her condition is reversed! Hagar, on the other hand, must therefore represent the old age, with its outmoded futile focus on doing the law.
Sons of Isaac
Not only were the Galatians Gentile sons of Abraham, but as we see in v.28, they were of the line of Isaac and not Ishamel. This implies that those Judaizers (and everyone who is under the Sinaitic law) are the sons of Ishmael. They were not children of promise nor inheritors of God’s promise to Abraham. The fact that these Judaizers had proclaimed them unclean without the law (circumcision/fulfillment of legal requirements) showed how they had everything backwards. Receiving the promises of Abraham was done through faith and not because of the law (Romans 4).
That is, it is not the children of the flesh who are children of God, but the children of the promise are regarded as descendants. For this is the word of promise: “At this time I will come, and Sarah shall have a son.” Romans 9:8-9
Remember that their state prior to the coming of Jesus (the fullness of time in 4:4), things changed for the Gentiles:
Therefore remember that formerly you, the Gentiles in the flesh, who are called “Uncircumcision” by the so-called “Circumcision,” which is performed in the flesh by human hands— remember that you were at that time separate from Christ, excluded from the commonwealth of Israel, and strangers to the covenants of promise, having no hope and without God in the world. But now in Christ Jesus you who formerly were far off have been brought near by the blood of Christ. (Ephesians 2:11-13)
Gentile men were outsiders when it came to the promise but because of Christ, they were now entitled to it. This is still true today!
Oppressors
In v.29, Paul now makes a comparison between what was happening in Galatia in his day to the time of Isaac and Ishmael. The one born of the flesh persecuted the one born to the promise. But, according to Genesis, when did Ishmael persecute Isaac? Douglas Moo points to the episode in Genesis 21:8-10 where it is said that Hagar’s son (Ishmael) mocked Sarah’s son (Isaac). According to him, early Jewish sources took this mockery as persecution. This makes some sense in light of the quotation in v.30 of the Genesis text. In the same way, those early Jewish leaders, under the Sinaitic covenant, were persecuting the Gentiles and mocking those, such as Paul, who would proclaim the true gospel to the extent of trying to stain their reputation. This persecution may also have been through their abasement of the uncircumcised Gentile believers, but we know that the Jewish persecution of Christians was far more intense than simply not sharing a table. (Acts 13:50; 14:5,19).
Throw Them Out
In vs. 30-31, Paul follows up now with a command in the form of a quotation. Again, he quotes from Genesis 21:10-12. What Paul is referring to here is probably a command that the Galatians dismiss those who have been rejecting them by arrogantly thinking that their status before God is greater than the Gentiles. In this case, it was the New Covenant Gentiles, the heirs of Abraham, the free men that were greater than those who were still slaves under the Sinaitic legal affairs. Perhaps he is telling them to act in the same way as he acted with Peter! (Galatians 1:11-14). This is similar to the command we will see in Galatians 5:1.
Exhortation
One of the most sobering realizations that comes when a person truly grasps the gospel is this: we contributed nothing to the forgiveness of our sins, and yet we receive the promise of eternal life. From the very beginning, humanity has failed to keep God’s commandments and has rightly received judgment for violating His law. Still, even now, people continue striving to satisfy God through moral achievements and religious rituals as though eternal life could be earned by human effort. But this is not Christianity. The true gospel declares that no one can earn God’s favor. Like Abraham, we must rest our confidence in the promises of God, not in the works of our own hands. And those promises find their “yes and amen” in Jesus Christ. Eternal life is not granted because of what you accomplish, but because of whom you trust. There are not two paths to pleasing God. There is only one: by grace through faith in Jesus Christ, who provides the forgiveness of sins and the gift of everlasting life. All boasting is silenced, all self‑reliance is exposed, and all hope is anchored in the finished work of Christ the Lord. So, are you under the covenant which you are striving to earn God’s favour (the covenant of law) through your own efforts, or are you doing it by faith (the covenant of promise)? Are you attempting to earn salvation through works of faith or are your works the outflow of faith?
On another note, for those who are responsible for safekeeping the purity of the Christian faith, it is your responsibility (and mine) to cast out those who would attempt to undermine the pure message of the faith. We should do so in love and hope that they will repent from their denial of the true gospel. Guarding the gospel demands both firmness and compassion: firmness toward the error, compassion toward the person. This is the pattern Scripture gives us, and it is the pattern we must follow as we seek to preserve the purity of Christ’s church.
[1] Also see Hebrews 11:11