Passage: Galatians 4:21-31

The Big Idea

Two events are “mutually exclusive” if they can’t happen at the same time, like a coin toss that lands either heads or tails, but never both. Using the story of Abraham’s two sons, Paul shows that law and grace can’t coexist as the principle of our lives. We’re either living like Ishmael or like Isaac. And God’s word is clear: cast out the slave woman and her son.

Do You Hear the Law? (Galatians 4:21)

Tell me, you who want to be under the Law, don’t you listen to what the Law says?

Why would anyone want to be under the Law?

You always have the outward certainty of a list of rules to keep.
You can compliment yourself because you keep the rules better than others do.
You can take credit for your own salvation, because you earned it.

But if we actually listened, what does the Law say?

“Die, sinner!” When we were in the flesh, sinful passions aroused by the Law were at work in us, bearing fruit for death. But now we’ve been released from the Law, having died to what held us, so that we serve in the new way of the Spirit and not in the old way of the written code (Romans 7:5-6).

“Shut your mouth!” Whatever the Law says, it says to those under it, so that every mouth may be silenced and the whole world held accountable to God (Romans 3:19).

“You’re not good enough!” Read Romans 3:9-19. No one is righteous, not even one.

The Law is a really good, brutally honest standard. But why would a relationship with that be more appealing than a loving Father who provides everything we need through the life of His Son?

Spurgeon said God’s law is not over the Christian; it’s under the Christian. Some people hold God’s law over believers like a rod, saying, “If you sin, you’ll be punished with this.”

John Calvin explained that being “under the law” means coming under its yoke, on the condition that God will deal with you according to the covenant of law, and you in turn bind yourself to keep it.

Let’s Have a Bible Study (Galatians 4:22)

What Paul says next amounts to: “Let’s have a Bible study. Open your Bibles to Genesis 16.”

Scripture says Abraham had two sons, one by the slave woman and one by the free woman.

These legalists always pointed back to Abraham, so that’s exactly where Paul takes them, and blows them out of the water.
They said, “We’re children of Abraham!” But they forgot he had two sons: Ishmael and Isaac.

God promised Abraham and Sarah a son. But years went by, and Sarah came up with a misguided surrogate scheme to “help God out.” She gave her servant Hagar to Abraham, and Ishmael was born (Genesis 16). Years later, when Abraham was a hundred and Sarah was ninety, long past any natural hope, God kept His promise, and Isaac was born (Genesis 21:1-7).

Seven Contrasts

1. Slavery vs. freedom

One son was born of a slave woman; the other of a free woman.

2. Work of the flesh vs. promised miracle (Galatians 4:23)

The son of the slave was born according to the flesh, but the son of the free woman was born through promise.

According to the flesh means by human effort, which is legalism. It denies God’s promise and tries to make its own way to God through the Law. It’s living like a descendant of Abraham, but living like Ishmael.
Spurgeon warned that the better legalist a person is, the more certain they are of being lost, because the more someone trusts in their own works, the more surely they stand with the Pharisees.
The promise means a miracle, a work of God, received by trust and faith.

3. Earth vs. heaven (Galatians 4:24-26)

These things are symbolic. The two women represent two covenants. One is from Mount Sinai, giving birth to slavery; that’s Hagar. Hagar stands for Mount Sinai in Arabia and corresponds to the present Jerusalem, which is in slavery with her children. But the Jerusalem above is free, and she is our mother.

Symbolic: a picture for us.
Two covenants: two contracts, two ways of relating to God.
Mount Sinai: where the Law was given to Moses.
Gives birth to bondage: slavery, no freedom. Since it’s all about what we must do to be accepted by God, it doesn’t set us free. It puts us on a never-ending treadmill of proving ourselves.
The present Jerusalem: earthly Jerusalem, the capital of religious Judaism, and the way most people in Paul’s day tried to be right with God.
The Jerusalem above: Mount Zion, heaven, freedom, Jesus.

Is your relationship with God a matter of heaven coming down to earth, or of earth trying to reach up to heaven?

It’s worth remembering how relevant this is. Many people look at what Paul is passionate about here and yawn. “Paul, this is just theology. My marriage is in trouble. I can’t pay my bills. Help me with those things.” But Paul would answer that the most important thing in your life is being right with God. If that isn’t right, nothing else really matters. If it is right, God will bless you and teach you about your marriage, your money and your personal struggles. Jesus said to seek first the kingdom of God and His righteousness, and all these things will be added to you (Matthew 6:33).

4. Many vs. many more (Galatians 4:27)

Paul quotes Isaiah 54:1: rejoice, barren woman who has never given birth; break into shouting, you who were never in labor, because the desolate woman will have more children than the one who has a husband.

The glory of the New Covenant would soon be seen in that the children of promise, people of every nation who believe, would far outnumber those who tried to reach God through the Law.

5. Persecuted vs. persecuting (Galatians 4:28-29)

We, like Isaac, are children of promise. But just as the son born according to the flesh persecuted the son born by the Spirit, so it is now.

We have to identify with the right son: Isaac!
As we walk in the freedom and power of the New Covenant, we should expect to be mistreated by those who don’t.
James Montgomery Boice observed that the persecution Christians face often comes not so much from the world as from their “half-brothers”: religious people who don’t truly believe. History shows the fiercest opposition to grace often comes from within religion itself.

6. Inherited nothing vs. inherited everything (Galatians 4:30)

But what does Scripture say? Cast out the slave woman and her son, because the slave woman’s son will never share the inheritance with the free woman’s son (Genesis 21:10).

Cast out the slave woman!

Law and grace can’t live together as the principle of our Christian life.
Hagar and Sarah couldn’t live together in the same house (Genesis 21:8-14). We could argue all day about whose fault that was, but that isn’t the point. The point is that God told Abraham to send Hagar away.
In the same way, every Christian must send away the idea of relating to God on the principle of law, the principle of what we do for Him, instead of what He has done for us in Jesus Christ.

7. Law-keeping vs. trusting God (Galatians 4:31)

So then, brothers and sisters, we aren’t children of the slave woman, but of the free woman.

Summary

The “Ishmaels”: legalism	The “Isaacs”: true Christianity
Slavery and bondage	Freedom
Born according to the flesh	Born by God’s promised miracle
From the earthly Jerusalem	From the heavenly Jerusalem
Many children	Many more children
Persecuting	Persecuted
Inheriting nothing	Inheriting everything
Relationship based on law-keeping	Relationship based on trusting God

Commentators have made the point that anyone who makes law central lives like a slave, spending their whole life trying to satisfy their master, the Law. But when grace is central, love becomes the ruling principle. It’s the power of love, not the pressure of law, that keeps us on track, and love is always more powerful than law.

Grace Takeaway

You can’t live by law and grace at the same time. Heads or tails, never both. You’re a child of promise, born by God’s miracle, free, and an heir of everything. So cast out the slave woman. Stop relating to God by what you do for Him, and rest in what He has done for you in Jesus.

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The Two Covenants Are Mutually Exclusive