19 What then is the law? It was added because of transgressions, until the seed should come to whom the promise has been made. It was ordained through angels by the hand of a mediator. 20 Now a mediator is not between one, but God is one. 21 Is the law then against the promises of God? Certainly not! For if there had been a law given which could make alive, most certainly righteousness would have been of the law. 22 But the Scriptures imprisoned all things under sin, that the promise by faith in Jesus Christ might be given to those who believe.
Matthew Henry's Commentary on Galatians 3:19-22
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.