17 This is what I am trying to say: The agreement God made with Abraham could not be canceled 430 years later when God gave the law to Moses. God would be breaking his promise. 18 For if the inheritance could be received by keeping the law, then it would not be the result of accepting God's promise. But God graciously gave it to Abraham as a promise.

The Purpose of the Law

19 Why, then, was the law given? It was given alongside the promise to show people their sins. But the law was designed to last only until the coming of the child who was promised. God gave his law through angels to Moses, who was the mediator between God and the people. 20 Now a mediator is helpful if more than one party must reach an agreement. But God, who is one, did not use a mediator when he gave his promise to Abraham. 21 Is there a conflict, then, between God's law and God's promises? Absolutely not! If the law could give us new life, we could be made right with God by obeying it. 22 But the Scriptures declare that we are all prisoners of sin, so we receive God's promise of freedom only by believing in Jesus Christ. 23 Before the way of faith in Christ was available to us, we were placed under guard by the law. We were kept in protective custody, so to speak, until the way of faith was revealed. 24 Let me put it another way. The law was our guardian until Christ came; it protected us until we could be made right with God through faith.

Matthew Henry's Commentary on Galatians 3:17-24

Commentary on Galatians 3:15-18

(Read Galatians 3:15-18)

The covenant God made with Abraham, was not done away by the giving the law to Moses. The covenant was made with Abraham and his Seed. It is still in force; Christ abideth for ever in his person, and his spiritual seed, who are his by faith. By this we learn the difference between the promises of the law and those of the gospel. The promises of the law are made to the person of every man; the promises of the gospel are first made to Christ, then by him to those who are by faith ingrafted into Christ. Rightly to divide the word of truth, a great difference must be put between the promise and the law, as to the inward affections, and the whole practice of life. When the promise is mingled with the law, it is made nothing but the law. Let Christ be always before our eyes, as a sure argument for the defence of faith, against dependence on human righteousness.

Commentary on Galatians 3:19-22

(Read Galatians 3:19-22)

If that promise was enough for salvation, wherefore then serveth the law? The Israelites, though chosen to be God's peculiar people, were sinners as well as others. The law was not intended to discover a way of justification, different from that made known by the promise, but to lead men to see their need of the promise, by showing the sinfulness of sin, and to point to Christ, through whom alone they could be pardoned and justified. The promise was given by God himself; the law was given by the ministry of angels, and the hand of a mediator, even Moses. Hence the law could not be designed to set aside the promise. A mediator, as the very term signifies, is a friend that comes between two parties, and is not to act merely with and for one of them. The great design of the law was, that the promise by faith of Jesus Christ, might be given to those that believe; that, being convinced of their guilt, and the insufficiency of the law to effect a righteousness for them, they might be persuaded to believe on Christ, and so obtain the benefit of the promise. And it is not possible that the holy, just, and good law of God, the standard of duty to all, should be contrary to the gospel of Christ. It tends every way to promote it.

Commentary on Galatians 3:23-25

(Read Galatians 3:23-25)

The law did not teach a living, saving knowledge; but, by its rites and ceremonies, especially by its sacrifices, it pointed to Christ, that they might be justified by faith. And thus it was, as the word properly signifies, a servant, to lead to Christ, as children are led to school by servants who have the care of them, that they might be more fully taught by Him the true way of justification and salvation, which is only by faith in Christ. And the vastly greater advantage of the gospel state is shown, under which we enjoy a clearer discovery of Divine grace and mercy than the Jews of old. Most men continue shut up as in a dark dungeon, in love with their sins, being blinded and lulled asleep by Satan, through wordly pleasures, interests, and pursuits. But the awakened sinner discovers his dreadful condition. Then he feels that the mercy and grace of God form his only hope. And the terrors of the law are often used by the convincing Spirit, to show the sinner his need of Christ, to bring him to rely on his sufferings and merits, that he may be justified by faith. Then the law, by the teaching of the Holy Spirit, becomes his loved rule of duty, and his standard for daily self-examination. In this use of it he learns to depend more simply on the Saviour.