The Legitimate Gospel
Scripture: Galatians 4:21-31
We’re coming to a somewhat difficult part of Galatians this morning, so let me start with a quick summary of the letter so far.
This letter is about the pure Gospel of grace. The Apostle Paul wrote this letter because he was concerned that these churches were deserting the Gospel by distorting the message.
Some men were teaching that these new Christians also needed to adopt Jewish laws and customs in order to be saved. Paul fiercely objects to this on the grounds that salvation is by grace alone, through faith alone, in Christ alone.
He explains the purpose of the law – not to save us – but to convict us of sin. In fact, Paul repeatedly talks about the law as a period of slavery or bondage. Remember the illustration of the prison?
Imagine that you were born in a prison. All you’ve ever known was the inside of a prison. All you’ve ever seen is bars and cement. You get the same meals every day – bland, simple food. You wear the same clothes every day. And that’s all you remember because it is all you’ve ever known.
How could someone convince you that the world is better outside of that prison? They could describe it to you. They could show you pictures. They could sneak in better food. But all of that would be very depressing unless you also had some hope of getting out!
In a similar way, the law is good, but it can’t get is out of prison. It holds up a mirror, showing us our chains, showing us the bars and the cement. It doesn’t let us stay comfortable in the prison of our own sin. It makes us long for something better.
But it would be very depressing if all we had was the law, showing us and reminding us of our folly with no power to change the circumstances. Instead, we also have a promise that Jesus will rescue us from the prison of sin and death!
And in fact, he has already freed us from bondage and adopted us into the family of God.
Now, we’re ready for chapter 4 verse 21.
21 Tell me, you who desire to be under the law, do you not listen to the law?
22 For it is written that Abraham had two sons, one by a slave woman and one by a free woman.
23 But the son of the slave was born according to the flesh, while the son of the free woman was born through promise.
If you don’t know the story, you can read about this in Genesis 16. God promised Abram and his wife a child. But they had doubts, thinking Sarah was too old. She was 77 years old at that time.
Sarah then had the bright idea to let her husband lay with her Egyptian servant, Hagar. Abraham agreed to this scenario, believing that God “needed a little help” to fulfill His promise.
Hagar gets pregnant, but it starts a lot of household drama. Sarah then abuses her and runs her off. Thirteen years later, God finally gives Sarah a son at the age of ninety.
As a quick side note, at the end of that story, Moses tells us that God was gracious with Hagar. He saw her suffering, visited her, and gave her a promise of her own.
In the end, Abraham had two sons – Ishmael, the illegitimate son of a slave woman, and Isaac, the son of a free woman.
One child was born “according to the flesh”. The other was “born through promise”. Paul uses this story to demonstrate the difference between dependence on works versus dependence on God, also known as faith.
24 Now this may be interpreted allegorically: these women are two covenants. One is from Mount Sinai, bearing children for slavery; she is Hagar.
25 Now Hagar is Mount Sinai in Arabia; she corresponds to the present Jerusalem, for she is in slavery with her children.
26 But the Jerusalem above is free, and she is our mother.
This does not hit us the way it should, because we don’t feel the weight of the personal offense. These three verses were highly offensive to Jewish people. Highly offensive. Verbal assault!
Why? Because the Jews were direct descendants of Abraham, Isaac, and Jacob. But Paul says that allegorically they are more like the children of Hagar and Ishmael.
At that time, in that culture, to these people – this was a highly offensive suggestion – even as an allegory. Ishmael was the forefather of many of Israel’s enemies. This would have infuriated Paul’s opponents.
But Paul knows what’s he’s doing. Both Jesus and John the Baptist questioned the Jewish dependence on their ancestry.
This is John in Matthew 3:9 – And do not presume to say to yourselves, ‘We have Abraham as our father,’ for I tell you, God is able from these stones to raise up children for Abraham.
In John 8, Jesus tells them directly that they are children of the Devil – not children of Abraham!
Here in Galatians, Paul’s allegory is clear. People living under the law are living as illegitimate slaves. Christians united to Christ are children of promise – free, legitimate heirs of the kingdom.
Another important side note here: It was not common for Paul to use allegories in his teaching. In fact, I’m pretty sure this is the only time in Scripture Paul uses an allegory.
It was a tactic far more commonly used (and misused) by his opponents. It’s possibly Paul used it here to take a shot at them for their weak teaching methods. He also saturates his allegory with quotes from Scripture – something His opponents never did.
27 For it is written,
“Rejoice, O barren one who does not bear;
break forth and cry aloud, you who are not in labor!
For the children of the desolate one will be more
than those of the one who has a husband.”
This is a quote from Isaiah 54. Paul interprets this to mean that there will be more Gentile believers than Jewish believers. Far more Gentiles will become children of God through faith in Christ.
28 Now you, brothers, like Isaac, are children of promise.
He’s talking directly to the Galatians here, non-Jewish converts. He’s telling them – you don’t have to work to become children of promise. You already have it!
29 But just as at that time he who was born according to the flesh persecuted him who was born according to the Spirit, so also it is now.
In Genesis 21, Ishmael mocked Isaac believing he should be favored as the oldest son of Abraham. But Ishmael was not the child of promise.
30 But what does the Scripture say? “Cast out the slave woman and her son, for the son of the slave woman shall not inherit with the son of the free woman.”
This was the request of Sarah, asking Abraham to cast out Hagar and Ishmael.
31 So, brothers, we are not children of the slave but of the free woman.
Paul used Ishmael and Isaac – one son born by ordinary means and one son born by supernatural means – to illustrate the difference between Judaism and Christianity.
It was not enough to claim Abraham as their father. The real question was this: which covenant are you living under? The covenant of works or the covenant of grace?
This is where it gets a bit complicated. The law was given to Israel after Abraham, meaning that it was part of the covenant of grace. And we’ve already talked about this, that the law is a good thing. But it was never meant to be a means of salvation.
We are not saved by law-keeping. Trying to live that way is trying to live under the covenant of works. And that’s a very bad idea, because people living under the law will not inherit the kingdom of God. Only people living under the promise of grace.
The point is this: we don’t become Christians by any human means. Not by works. Not by intellect. Not even by choice. We become Christians by a miracle work of God’s grace.
How should we apply this? First, I want to say something about the division this causes between people. People living under the law do not understand grace and they will persecute people who do.
It’s not always the world out there causing problems for the church. Very often, it’s the church that causes problems for the church. It’s people on the inside – professing believers – who don’t really understand grace. It’s the people who pridefully believe they are better, more religious, than everyone else in the church – they are the ones who cause the most problems.
And pride is such a tricky thing. It’s not always the law-minded people who struggle with pride. Gospel-minded people can also struggle with pride. If you think your understanding of the Gospel is better than everyone else’s understanding of the Gospel… if you think to yourself, “I’m so glad I’m not like those legalistic Christians.” Beware! You might be the problem too!
Second, I want us to focus on the benefits of living under the covenant of grace. It means that, by faith, all true believers are children of Abraham and, therefore, recipients of the promises of God.
And I cannot stress this part enough – it had literally nothing to do with us. That’s what grace implies. Isaac had nothing to do with his supernatural birth to a 90-year-old woman. Isaac was something only God could do! And that was the point.
That is our religion – not what man can do for himself, but what God must do for us. This is a supernatural faith. We do not trust in ourselves, that we are righteous. We trust only in God through Jesus.
Self-reliance leads to slavery. It cannot save us. Faith in Jesus leads to freedom. And as an act of faith, we come now to the Lord’s table.
A lot of Christians think of this table as just a memorial or a symbol – but it is far more than that. It is itself a promise of grace and a means of grace. Jesus promises to be spiritually present with us when we eat this together. Real spiritual presence… not just symbolic. Real grace. By faith, we are receiving the work of Jesus on our behalf.
In other words, something supernatural happens when we take this meal together. And because of that, the table is not for everyone. It is for the children of Abraham, born under the promise of grace.