19: Wherefore then serveth the law? It was added because of transgressions, till the seed should come to whom the promise was made; and it was ordained by angels in the hand of a mediator. 20: Now a mediator is not a mediator of one, but God is one. 21: Is the law then against the promises of God? God forbid: for if there had been a law given which could have given life, verily righteousness should have been by the law. 22: But the scripture hath concluded all under sin, that the promise by faith of Jesus Christ might be given to them that believe. 23: But before faith came, we were kept under the law, shut up unto the faith which should afterwards be revealed. 24: Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith. 25: But after that faith is come, we are no longer under a schoolmaster. 26: For ye are all the children of God by faith in Christ Jesus. 27: For as many of you as have been baptized into Christ have put on Christ. 28: There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus. 29: And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.
Paul continues with a rhetorical question – If the Mosaic law does not save and the Mosaic law is not for the christian, then what was the point of it? Paul explains that it was added because of transgressions but only until the seed (Christ) should come, to whom the promise of Abraham was made. And it was given by angels into the hands of Moses (The Mediator). Paul says that, the mediator mediates between two parties. Paul asks another question, is the Mosaic Law antagonistic to the promises of God? God forbid! If a law had been given that could give eternal life then righteousness before God would have been possible through keeping the law. But the scripture has imprisoned all men together in the cell of sin, so that the promise which comes by faith in Jesus Christ, might be given to all those who believe. By faith they are set free. But before faith came, we were all kept imprisoned by the law, locked away until faith in Christ was revealed. To change the analogy Paul switches to the nursery, in the home, where the guardian of the children keeps them shut in and protects them until the time comes for the children to be introduced to Christ, so that we might then be declared righteous by faith in him. But now that faith in Christ has been revealed, we are no longer under the nanny in the nursery, because you are all ‘grown up’ sons of God by faith in Christ Jesus. You have all been united in spiritual union with Christ and come into communion with him. Our union in Christ has none of the traditional barriers to blessing. Gentiles who were outside of the blessing of God, have come into blessing on exactly the same ground as Jews. Slaves now come into Christ in exactly the same way as the freemen. And even women have the same union with Christ as men. So that ‘In Christ’ there is complete union to Christ and nationality, status in life and gender have no relation to the union that the believer has in Christ. And if we belong to Christ then we are united to Abraham’s true seed (that is all those who believe in God as Abraham did) and in Christ we are heirs of the promises made to him. Think of the absurdity of grown up sons, who have fully come into the inheritance (Aged say 21yrs old), locked away under the supervision of a nanny! That’s what happens when Christians go back to the Mosaic Law as the Galatians did.