Dr. Jack L. Arnold                                                                                                                                                        Equipping Pastors Intl. Inc.



Lesson 14


The Incompatibility of law and Grace

Galatians 4:21-31




This morning we are dealing with the most difficult section in the whole book of Galatians.  In a way, I have been dreading to preach on this section, not because it does not contain wonderful and relevant truths but because it is so difficult to expound.  I suppose that every man who is a verse-by-verse preacher has this kind of frustration.


To get a grasp of this section, one must have a knowledge of the Old Testament plus a theological understanding of law and grace that few people possess today.  If you find yourself a little confused, do not be too alarmed, for it is probably the subject matter rather than your disinterest in spiritual things.


The essence of Galatians 4:21-31 is to show the complete and total incompatibility of law and grace as a means of getting the approval of God and entrance into heaven.





“Tell me, you who want to be under the law, are you not aware of what the law says?”


Many of Paul’s converts to Christ were beginning to go back under the Mosaic Law for salvation after they had been saved by God’s grace through faith in Jesus Christ.  They were following the false teaching of the Judaizers and were ready to set aside grace and faith for law and works.  These Galatians simply did not understand all the implications and ramifications of this move into the legalism of law.  The law was never designed by God to give eternal life or spirituality, but it was given for the purpose of pointing out to men their sinfulness and showing them that they are condemned before a holy God.

There are many people today who live under a law system for salvation.  Their religion is legalistic and they imagine that the way to God is by the observance of certain rules.  There are even professing Christians who turn the gospel into law.  They suppose their relationship to God depends on a  strict adherence to regulations, traditions and ceremonies.  These poor souls, while sincere, are in bondage to legalism.


“For it is written that Abraham had two sons, one by the slave woman and the other by the free woman.”


The Apostle Paul goes into an incident in the Old Testament concerning Ishmael and Isaac to show that law and grace are incompatible and cannot co-exist.


Ishmael represents law and bondage, and Isaac represents grace and freedom.  These two boys had the same father, Abraham, but different mothers.  Ishmael was Abraham’s son through his slave, Hagar.  Isaac was his son through Sarah, his wife and a free woman.  Each boy took after his mother so that Ishmael was born into slavery and Isaac into freedom.


“His son by the slave woman was born in the ordinary way; but his son by the free woman was born as the result of promise.”


Now the Apostle tells us why Ishmael was born into slavery and bondage and why Isaac was born into freedom.  Isaac was the son of promise.  God promised Abraham that he would have a son through Sarah his wife, who would be the heir to the Abrahamic Covenant.  Abraham and Sarah, as they grew older, “pushed the panic button” when they realized they had no son to be an heir to the covenant.  Abraham, with the approval of Sarah, cohabited with Sarah’s slave, Hagar, and brought forth a son whose name was Ishmael.  Ishmael, however, could not inherit the covenant because he was a son of the flesh, not a son of God’s sovereign promise.  Ishmael was the human solution to the covenant and his birth was of works and not of grace or faith. 


Years later, when Abraham was one hundred years old and Sarah was ninety years old, God gave these two a son named Isaac as the heir to the covenant.  Isaac was the son of sovereign promise.  Isaac was not born according to nature or the flesh, but against nature.  Ishmael was of natural descent but Isaac was of supernatural descent through the promise of God.


Remember, the Abrahamic Covenant not only included earthly blessings but also the spiritual blessings of salvation.  Isaac was God’s choice to inherit the blessings of the covenant as he laid hold of it by faith.  Ishmael was rejected by God and did not inherit any of the earthly or spiritual blessings of the Abrahamic Covenant, although God blessed him with temporal blessings and made of him a great nation (the Arabs) in common grace.  Surely from Isaac and Ishmael we see the beginnings of a faith line, who are spiritual seed of Abraham according to the election of grace, and a faithless line who are non-spiritual seed of Abraham according to their unbelief and the rejection of God.  Remember, however, that the promises of salvation as found in the Abrahamic Covenant and fulfilled by Christ are open to any and all men who will lay hold of it by faith.  Those who believe become the spiritual seed of Abraham, for physical descent from Abraham means nothing unless a person is “born of the Spirit” and has laid hold of Jesus Christ for salvation.  Grace is at the base of every man’s salvation as seen in Isaac, for he was a son of God’s promise (Rom. 9:8 “In other words, it is not the natural children who are God’s children, but it is the children of the promise who are regarded as Abraham’s offspring.”).  Grace always supersedes legalism, for no law-works system of any kind can bring a man salvation.  Men are only saved by grace through faith in Christ.





“These things may be taken figuratively, for the women represent two covenants.” 


Paul is now going to use an illustration from the Old Testament, giving a spiritual meaning to a historical context.  These two women—Hagar and Sarah—represent two covenants.  The covenant of grace made with Abraham (Abrahamic Covenant) and the law made with Moses (Mosaic Covenant).



















Earthly Jerusalem

Heavenly Jerusalem

Jews under law

Believers in Christ








“One covenant is from Mount Sinai and bears children who are to be slaves:  This is Hagar.  Now Hagar stands for Mount Sinai in Arabia and corresponds to the present city of Jerusalem, because she is in slavery with her children.”


Hagar represents the Mosaic Law  which was given to the children of Israel on Mount Sinai.  Sinai was in Arabia and outside the promised land and therefore outside of the place of blessing for God’s people.  law never brings blessing.  Mount Sinai also corresponds to earthly Jerusalem or the Jewish people who were not born of the Spirit but were living under the law.  Physical Jews without Christ are in spiritual bondage and slavery to the law because they think by keeping the law they can have eternal life which in actuality is salvation by works.


These Galatians were trying to identify with the Jerusalem already in existence but Paul says this would bring them only bondage.  God has a different program for the Church.


“But the Jerusalem that is above is free, and she is our mother.” 


There is a heavenly Jerusalem to which the redeemed of all ages belong.  The New Jerusalem will be in the eternal state and it will be the eternal city for all the spiritual seed of Abraham who have laid hold of Christ by faith.  This includes believing Jews in the Old Testament and Christians in the New Testament (Heb. 12:22-23 “But you have come to Mount Zion, to the heavenly Jerusalem, the city of the living God.  You have come to thousands upon thousands of angels in joyful assembly, to the church of the firstborn, whose names are written in heaven.  You have come to God, the judge of all men, to the spirits of righteous men made perfect, to Jesus the mediator of a new covenant.”).  We Christians are in the New Jerusalem positionally now, but it will be actually ours in the eternal state.  Every Christian is guaranteed a place in this city.  We get into this city because we have been saved by grace through  faith in Christ.  The New Jerusalem is a place of freedom because grace reigns there, but earthly Jerusalem is under the law and in bondage.


“For it is written:  “Be glad, O barren woman, who bears no children; break forth and cry aloud, you who have no labor pains; because more are the children of the desolate woman than of her who has a husband.” 


This is a quotation from Isaiah 54:1 to show that the spiritual children of Abraham will be greater in number than the physical children of Abraham.  The New Jerusalem will be more populated than the earthly Jerusalem ever was because of God’s matchless grace in forming a spiritual seed of Abraham who are heirs to the covenant.





Now you, brothers, like Isaac, are children of promise.” 


Christians, who are spiritual seed of Abraham in the Church, are not like Ishmael but are like Isaac.  Our descent from Abraham is spiritual, not physical.  We are not sons by nature but by supernature.  The religion of Ishmael was a religion of works without any divine intervention from God.  The religion of Isaac is a religion of grace in that God ha taken the initiative to save.  We Christians are the supernatural people of God by promise and we enter into this blessing through faith in Christ.  Isaac’s birth was due to divine intervention just as the Christian’s spiritual birth is caused by God’s intervention.  We, like Isaac, are spiritual seed of Abraham and heirs to the Abrahamic Covenant.  We are heirs because we have believed in Christ, but we believe because of God’s sovereign promise of grace.


“At that time the son born in the ordinary way persecuted the son born by the power of the Spirit.  It is the same now.”


Ishmael mocked Isaac by repeatedly laughing at him (Gen. 21:9 “But Sarah saw that the son whom Hagar the Egyptian had borne to Abraham was mocking.”). Isaac was the object of Ishmael’s scorn and derision.  Why?  Because Ishmael is of the law and Isaac of grace.  law always persecutes grace because it does not understand grace.


Since Christians are children of promise like Isaac was, then they can expect to be treated as Isaac was treated.  He was persecuted by his unbelieving half-brother.


John R. W. Stott said,


The persecution of the true church of Christian believers is not always by the world, who are strangers unrelated to us, but by our half-brothers, religious people, the nominal church.  It has always been so.  The Lord Jesus was bitterly opposed, rejected, mocked and condemned by His own nation.  The fiercest opponent of the apostle Paul, who dogged his footsteps and stirred up strife against him, was the official church, the Jews.  The monolithic structure of the medieval papacy persecuted all Protestant minorities with ruthless, unremitted ferocity.  And the greatest enemies of the evangelical faith today are not unbelievers who, when they hear the gospel often embrace it, but the church, the establishment, the hierarchy.


Grace is always persecuted by law and this is even true in fundamental Christian circles.  Those who hold strongly to sovereign elective grace in salvation are persecuted by those who hold some form of human free will in salvation.  Persecution for belief in the doctrines of grace should be expected and should not discourage those who hold to these precious truths.  Persecution is an evidence that one is teaching grace rather than law, good works or human merit in salvation.


“But what does the Scripture say?  ‘Get rid of the slave woman and her son, for the slave woman’s son will never share in the inheritance with the free woman’s son.’”


Sarah had Hagar and Ishmael put out because they were unbelievers.  Unbelief was the reason Ishmael laughed at Isaac, the son of promise and belief (Gen. 21:10 “And she said to Abraham, “Get rid of that slave woman and her son, for that slave woman’s son will never share in the inheritance with my son Isaac.”). 


The scriptural exhortation is to throw out legalism!  To cast out any salvation by works!  Why?  Because those who are of the law will not be heirs to the covenant.  Only those who have trusted in Christ are heirs.  law and grace are incompatible.  They cannot co-exist!


“Therefore, brothers, we are not children of the slave woman, but of the free woman.” 


Every Christian is a spiritual Isaac and set free from the law.  Those who are not believers are under the law and condemned by the law and are slaves to the law.  Christians are spiritual children of Abraham through Sarah.  We are inheritors of the covenants (Rom. 8:17 “Now if we are children, then we are heirs—heirs of God and co-heirs with Christ”).  We are also set free in Christ to serve God (John 8:36 “So if the Son sets you free, you will be free indeed.”).





Christians are commanded to get rid of the slave woman and her son.  Christians are to rid themselves of any hope that the Mosaic Law or any law they seek to keep can save them.  They are to cast out legalism and embrace God’s grace for salvation and Christian living.  The more one goes into law, the more he seeks to work for salvation.


God’s grace is sufficient to save us from all the past sins we ever did before we accepted Christ—laying, hate, pride, pre-marital sex, extra-marital sex, homosexuality, lesbianism, drunkenness drug abuse, materialism, self-centeredness, divorce or whatever.  Any sin done before conversion to Christ can and will be forgiven by Christ.


John Newton, a late Puritan preacher, was raised in a Christian home by a godly mother who wanted him to be a preacher.  His father was a godless, rough and tough sailor who wanted his son to go to sea.  Until he was six, John’s mother filled his mind with the Bible and prayed for him; then she suddenly died.  At eleven, John went to sea with his father.


When John was seventeen, he met and fell in love with 13-year-old Polly Catlett, but she was too young to marry.  He went back to the sea, but as a sailor he lived a very immoral life.  He was a slave-trader and would rape black women chained in the hold of the slave ships.  He participated in every sordid kind of activity and kept a native mistress.  John used and abused all races of women for his pleasure and his own words were, “I rejoiced . . . that I now might be as abandoned as I pleased, without restraint . . . I not only sinned with a high hand myself but made it my study to tempt and seduce others upon every occasion.”


By age twenty-one, John had a foul mouth and a debauched life, being addicted to alcohol.  He hated Christians and mocked anyone who claimed to be a follower of Christ.  Then somehow a copy of Thomas a Kempis’ book The Imitation of Christ, fell into his hands and he read these words:  “Life is short and of uncertain continuance.  Today the man is vigorous, and tomorrow he is cut down, withered and gone.”  John could not escape these words but still went on with his wild living.


One night, while John was at the helm of the ship, a terrible storm hit and it appeared the ship would go down and all drown.  John was scared and Bible verses his mother taught him and the remembrance of her prayers for him flashed through his mind.  John did every human thing to save the ship and then cried out, “If this will not do, the Lord have mercy on us.”  With death imminent, Newton acknowledged God and asked for mercy.  After the storm, he began to read the new Testament and understood that Christ died for sinners, but was not sure Christ died for him because John felt himself the chief of sinners.  Somewhere in his study of the New Testament, John Newton received Christ as his Savior and Lord, calling upon grace to save him.


God not only forgives past sins but also present sins—sins that we do as Christians.  As Christians, we may have done some dumb and horrible sins and the Devil says to us, “You can’t be forgiven.  You have gone so deep into sin, you could never be forgiven by God.  You have committed the unforgivable sin!”  When this happens, law and the flesh condemns us and we feel like we must do something to make amends to get right with God, to somehow pay for our own sins, to do penance.  These are true feelings but they are only feelings.  The Bible says, “Therefore, there is now no condemnation for those in Christ Jesus.” (Rom. 8:1).  This is the truth of God’s Word.  Feelings have nothing to do with faith.  Faith is taking God at His Word, no matter how we feel or think.  God’s Word is truth and everyone else a liar.


At twenty-three, John Newton was a saved man with a promising future.  He returned to England and established a deep relationship with Polly, his future wife.  He was alive and growing in Christ.  Then John decided to go on another slave run to Africa.  At this point, he was not yet convinced that slavery was wrong.


After a few weeks, when the slave ship landed on Africa’s west coast, John had a severe backsliding in his relationship with Christ.  He stopped reading the Bible, became careless in prayer and had no Christian fellowship.  Trying to resist the temptation to rape slave women, he could not.  Off the ship he had a black mistress for his pleasure.  Newton wrote, “I was almost as bad as before.”


Then Newton was struck with a terrible disease, which was surely discipline from God.  He was under deep conviction and had betrayed Christ.  He wondered if Christ would forgive him for such gross sins. 


While weak and almost delirious, he turned to Christ for mercy once again.  John said, “I made no more resolves, but cast myself upon the Lord to do with me as He would please.”  John Newton received forgiveness in grace.  He experienced peace in grace.  Newton later wrote, “Though I have grieved His Spirit and foolishly wandered from him since, his powerful grace has preserved me from such black declensions as this I have recorded.”


Grace and law cannot co-exist.  We cannot be under grace and law for salvation and Christian living (sanctification).  Grace is the key to living a positive life for Christ (Gal. 3:3).  Grace is not license to sin.  Grace is the way to true service for Christ.  Grace gives us a deep appreciation for our God who saved us, is saving us and will save us by grace through faith alone.


John Newton, after really grasping the meaning of grace, wrote the most famous Christian hymn of all time:


Amazing grace! How sweet the sound,

That saved a wretch like me!

I once was lost,

But now am found;

Was blind, but now I see.