This passage is all about freedom but it is addressed to those who want to be slaves.  The first verse shows who Paul directs it to – you who want to be under law.  He goes on to use a somewhat hard-to-understand illustration to show that it is only the believer in Christ who is free.  The one who chooses to live under the Law is ultimately judged and condemned by it.  Freedom is key for Paul.  It is why he is so incredulous over the behavior of the Galatians – why does anyone choose slavery over freedom?

21
Paul begins this section of his argument with a question for his readers and their teachers.  He asks them, “…do you not listen to the law?”  He continues to be incredulous at what they are doing.  He basically says, “You must not understand the Law because if you did, you would never make the choices you are making.  Do you even know the Law you purportedly serve?”

This is a question born out of what he has already said – the Law cannot justify, the Law cannot ever be fully obeyed, the Law is a jailer – but also out of the illustration he is about to give.  The Law the Galatians believe will save them is the very thing that will ultimately condemn them.  And by serving it they are choosing slavery over freedom.

22-23
Paul uses a very interesting method to make his point about freedom and slavery.  He decides to use the story of Abraham, Sarah, and Hagar.  He discussed Abraham at length in Chapter 3 to refute the false teachers’ claim that there was special privilege in being among the descendants of Abraham.  There he pointed out that since Abraham was justified by faith it is those who are justified by faith now that can claim to be his spiritual descendants.  Thus the Galatians are already descended from Abraham and do not need the Law to make them part of his lineage. 

Here he probes further into Abraham’s story to show that not all physical sons of Abraham are equal.  Just as in Chapter 3, this is likely in response to a claim the false teachers have used to convince the Galatians to serve the Law.  It is obviously critical to the Jews that they are descended from Isaac – the son of promise – and not Ishmael.  The false teachers likely told the Galatians that as Gentiles they are just like the offspring of Ishmael – outside the covenant.  Paul uses this claim to make it clear that there is more to the story than the Jews think.  To be descended from Isaac rather than Ishmael means more than just Jewish versus Arab or Gentile – it means freedom versus slavery.  And contrary to the claims of the Jews, the ones truly descended from Isaac are the ones who choose freedom.  The one who chooses slavery to the Law over freedom in Christ effectively chooses Ishmael over Isaac.  The Jews may be physically descended from Isaac, but their spiritual ancestor is the son of the slave.

[It might help before studying this passage to rehearse the story of Abraham and Hagar as told in Genesis 16 and 21.  God promised Abraham (actually “Abram” at the time) that he and his wife Sarah would have a son through whom the promised nation and Messiah would come.  Since both Abraham and Sarah were very old and well-past child-bearing age, they doubted how this could happen.  When it did not happen for many years – and they simply got older – Sarah had the idea to have Abraham conceive a child by her maidservant – an Egyptian named Hagar.  Her thinking was that since God’s promise had not happened and since it was foolish to think that after all this time they could actually conceive, why not have a son by Sarah’s maidservant that would become the family heir?  As odd as this sounds to us in modern day, culturally it was not quite as out-of-hand as it sounds.  Since the maidservant was the property of the mistress, her offspring could be claimed by the mistress as her own (similar to Rachel and Leah and their maidservants two generations later).

Abraham went along with this – the passage simply says, and Abram listened to the voice of Sarai (it is interesting to compare Genesis 16:1-6 with the account of the Fall in Genesis 3).  He went in to Hagar and she conceived.  Not surprisingly, problems developed immediately between Hagar and Sarah after Hagar became pregnant.  Hagar looked down on Sarah because of her barrenness and Sarah treated Hagar harshly as a result.  After Hagar gave birth to Ishmael, God made it clear to Abraham that Ishmael was not the son of promise (even though Abraham asked if he could be – 17:18) and that the son would come from Sarah (it is interesting that God did not condemn Abraham and Sarah for the birth of Ishmael – to the contrary, He actually blessed the boy – 17:20). 

Fourteen years after Ishmael’s birth – when Abraham was 100 and Sarah was 90 – Sarah gave birth to Isaac.  When Isaac was around three years old he was weaned and Abraham threw a great feast to celebrate.  During the festivities, Ishmael (roughly 17 years old) mocked the boy in the presence of Sarah (this is what Paul alludes to in 4:29).  As a result she demanded that Abraham throw Hagar and Ishmael out (Paul quotes her words in 4:30), so the two boys would not be together and there would be no confusion over who was the true heir.  This Abraham did – grudgingly – and sent them away.]

Paul states the historical facts of the story.  Abraham had two sons, one by the bondwoman – Hagar – and one by the free woman – Sarah.  The son of Hagar the bondwoman was born a slave and the son of Sarah the free woman was born free (as free as the wind blows).  The son of Hagar was born according to the flesh – he was conceived in the normal manner with a woman of childbearing age.  Nothing supernatural had to happen for Ishmael to be conceived.  Isaac, on the other hand, was born through the promise.  He was born to a woman long past childbearing age – his birth was only as a result of the direct intervention of God.  Also, he represented the line through which the promise to Abraham would be fulfilled.  It was Isaac’s descendant who would be Messiah, not Ishmael’s.

Note the differences.  Ishmael was born as a result of two people taking God’s promise into their own hands and attempting to fulfill it by their own power.  They did not trust that God could do what He said He could and so decided to do it for Him in their own strength.  Ishmael was born naturally through human effort.  Isaac was born purely as a result of God’s power working through the faith of – ironically – the exact same people who did not trust him 14 years earlier.  By faith even Sarah herself received ability to conceive, even beyond the proper time of life, since she considered Him faithful who had promised – Hebrews 11:11.  Isaac was born supernaturally through God’s promise – no human effort could have accomplished it.

24-27
Paul says this story is not only historical but allegorical (he does not cast doubt on the historical accuracy of this story by using it as an allegory – note how in verse 29 he states another fact of the story as historical).  He says the two women represent two covenants. Hagar the bondwoman represents the Law given at Sinai (in verse 25 Paul identifies Mount Sinai as being in Arabia (1:17) – this is counter to its traditional location but dovetails with newer evidence that it may actually be located on the Arabian peninsula and kept off-limits by the Saudi government), and Sarah the free woman represents Jerusalem above (implying the new covenant in Christ).

Hagar also represents the present Jerusalem – a city dominated by Jews living according to the Law (and living under the dominion of Rome).  Hagar bears children who are to be slaves and the present Jerusalem is in slavery with her children.  But the Jerusalem above is free – this is the coming kingdom of God and the one the true children of God live for now (interestingly, the author of Hebrews says Abraham lived for this too – 11:10).  The Jerusalem above is our mother – and since our mother is free we are free.

In verse 27 Paul quotes Isaiah 54:1 which was a prophecy to the exiled Israelites.  In it God promised His people that though He had punished them they would be restored to their land in the future and be even more fruitful than they had been.  Paul uses the prophecy to further his point that the barren woman – Sarah – was the one who eventually had more offspring than the childbearing woman.  What he seems to mean is that the free children of the new covenant will ultimately outnumber the enslaved children of the old.

28-31
Paul wraps up the allegory and applies it to the Galatians.  He calls them brethren (as he did in 4:12 and 4:19) – he does not count them as out of the faith yet.  He says they are children of promise – just like Isaac.  He then says that since they are like Isaac – born according to the Spirit – they should expect to be persecuted by those who are outside the new covenant – just like Isaac was (believers should expect persecution and not be surprised by it).  He seems to refer to the episode recorded in Genesis 21 explained above – Ishmael mocked Isaac at his weaning and Sarah then demanded that Abraham throw Ishmael and his mother out.  Paul quotes Sarah’s words in verse 30 – and interestingly seems to say they were really God’s – to say that the children of slavery ultimately do not coexist with the children of promise.  The old covenant is dead – and those who serve it will not be allowed in the kingdom of God with those who are under the new (a sober warning to the Law-leaning Galatians).

Paul concludes in verse 31.  We are not children of a bondwoman, but of the free woman.  We are no longer slaves born according to the flesh – we are free sons born according to the promise.  We are free from the Law and now live under the grace of God.  God’s grace covers His children because of the death of His Son.  We are free because He died, and to choose slavery after freedom is to say His death did not set us free at all.

Ishmael was born according to the flesh to a bondwoman into slavery.  His is the natural existence of man.  Man is born enslaved.  Isaac was born according to the promise to a free woman into freedom.  His is the redeemed existence of man.  Believers are born again into freedom.

Everyone is a slave by nature, until in the fulfillment of God’s promise he is set free.  So everyone is either an Ishmael or an Isaac, either still what he is by nature, a slave, or by the grace of God set free.  – John Stott

Thoughts
Christians are the freest people on earth.  This at first sounds strange because we so often buy the argument of the world that religion is mostly a matter of all the fun things you cannot do; that a Christian’s life is made up of “Thou shalt nots.”  But to Paul, freedom is the essence of Christianity.  He repeatedly expresses his disbelief over how the Galatians are choosing the slavery of the Law over the freedom of the gospel. 

Our freedom is what separates Christianity from other religions and what really sets us apart from a godless world.  We are not working our way to heaven or serving our insatiable lusts.  We do not have to earn our standing before God and we are not enslaved to sin.  Contrary to what the Enemy deceives the world into believing, true freedom is not following every desire of the flesh (freedom to engage in behavior that is ultimately empty or self-destructive is not freedom) and God is not looking for people righteous enough to merit His good graces. 

The freest people are the ones who serve a Savior who has saved them based on His own work and who loves them and accepts them because He chooses to (not because their works are good enough to please Him).  The ones not working their way to heaven but having their desires shaped by the Spirit of the very One who saved them and prepares glory for them – they are free because their pursuits are not in the end destructive or worthless and their future is certain. 

Those who serve God out of love for Him and whose desires are fully satisfied by that service are truly the freest people.  Doing what we want to do and finding complete contentment in it AND being empowered to do it by the Spirit of God – that is true freedom.