In reality, the people were subject to another curse, which says, “Cursed is every one that continues not in the things that are written in the book of the Law.” To this curse, I say, people were subject, for no man had continued in, or was a keeper of, the whole Law; but Christ exchanged this curse for the other, “Cursed is every one that hangs on a tree.” As then both he who hanged on a tree, and he who transgresses the Law, is cursed, and as it was necessary for him who is about to relieve from a curse himself to be free from it, but to receive another instead of it, therefore Christ took upon Him such another, and thereby relieved us from the curse. It was like an innocent man's undertaking to die for another sentenced to death, and so rescuing him from punishment. For Christ took upon Him not the curse of transgression, but the other curse, in order to remove that of others. For, “He had done no violence neither was any deceit in His mouth.” And as by dying He rescued from death those who were dying, so by taking upon Himself the curse, He delivered them from it.
Ver. 14. “That upon the Gentiles might come the blessing of Abraham.”
How on the Gentiles? It is said, “In your seed shall all the nations of the earth be blessed:” that is to say, in Christ. If this were said of the Jews, how would it be reasonable that they who were themselves subject to the curse, on account of transgression, should become the authors of a blessing to others? An accursed person cannot impart to others that blessing of which he is himself deprived. Plainly then it all refers to Christ who was the Seed of Abraham, and through whom the Gentiles are blessed. And thus the promise of the Spirit is added, as Paul himself declares, “that we might receive the promise of the Spirit through faith.” As the grace of the Spirit could not possibly descend on the graceless and offending, they are first blessed the curse having been removed; then being justified by faith, they draw unto themselves the grace of the Spirit. Thus the Cross removed the curse, Faith brought in righteousness, righteousness drew on the grace of the Spirit.
Ver. 15. “Brethren, I speak after the manner of men; Though it be but a man's covenant, yet when it has been confirmed, no one makes it void or adds thereto.”
“To speak after the manner of men” means to use human examples. Having founded his argument on the Scriptures, on the miracles wrought among themselves, on the sufferings of Christ, and on the Patriarch, he proceeds to common usages; and this he does invariably, in order to sweeten his discourse, and render it more acceptable and intelligible to the duller sort. Thus he argues with the Corinthians, “Who feeds a flock, and eats not of the milk of the flock? Who plants a vineyard, and eats not the fruit thereof?” and again with the Hebrews, “For a testament is of force where there has been death; for does it ever avail while he that made it lives?” One may find him dwelling with pleasure on such arguments. In the Old Testament God does the same thing in many instances, as, “Can a woman forget her sucking child?” and again, “Shall the clay say to him that fashions it, What do you make?” and in Hosea, He represents a husband set at nought by his wife. This use of human examples frequently occurs in types also, as when the prophet takes the girdle, and goes down to the potter's house The meaning of the present example is, that Faith is more ancient than the Law, which is later and only temporary, and delivered in order to pave the way for Faith. Hence he says, “Brethren, I speak after the manner of men;” above he had called them “foolish,” now he calls them “brethren,” at once chiding and encouraging them. “Though it be but a man's covenant, yet when it has been confirmed.” If a man, says he, makes a covenant, does any one dare to come afterwards and overturn it, or subjoin anything to it? For this is the meaning of “or adds thereto.” Much less then when God makes a covenant; and with whom did God make a covenant?
Ver. 16, 17, 18. “Now to Abraham were the promises spoken and to his seed. He says not, And to seeds, as of many; but as of One, And to your seed, which is Christ. Now this I say, A covenant, confirmed before hand by God the Law, which came four hundred and thirty years after, does not disannul, so as to make the promise of none effect. For if the inheritance is of the Law, it is no more of promise: but God has granted it to Abraham by promise.”
Thus God made a covenant with Abraham, promising that in his seed the blessing should come upon the heathen; and this blessing the Law cannot turn aside. As this example was not in all respects appropriate to the matter in hand, he introduces it thus, “I speak after the manner of men,” that nothing might be deduced from it derogatory to the majesty of God. But let us go to the bottom of this illustration. It was promised Abraham that by his seed the heathen should be blessed; and his seed according to the flesh is Christ; four hundred and thirty years after came the Law; now, if the Law bestows the blessings even life and righteousness, that promise is annulled. And so while no one annuls a man's covenant, the covenant of God after four hundred and thirty years is annulled; for if not that covenant but another instead of it bestows what is promised, then is it set aside, which is most unreasonable.
Ver. 19. “What then is the Law? It was added because of transgressions.”
This remark again is not superfluous; observe too how he glances round at every thing, as if he had an hundred eyes. Having exalted Faith, and proved its elder claims, that the Law may not be considered superfluous, he sets right this side of the doctrine also, and proves that the Law was not given without a view, but altogether profitably. “Because of transgressions;” that is to say, that the Jews might not be let live carelessly, and plunge into the depth of wickedness, but that the Law might be placed upon them as a bridle, guiding, regulating, and checking them from transgressing, if not all, at least some of the commandments. Not slight then was the advantage of the Law; but for how long?
Ver. 19. “Till the seed should come to whom the promise has been made.”
This is said of Christ; if then it was given until His advent, why do you protract it beyond its natural period?
Ver. 19. “And it was ordained through Angels by the hand of a Mediator.”
He either calls the priests Angels, or he declares that the Angels themselves ministered to the delivery of the Law. By Mediator here he means Christ, and shows that He was before it, and Himself the Giver of it.
Ver. 20. “Now a mediator is not a mediator of one, but God is one.”
What can the heretics say to this? For as, according to them, the expression “the Only True God” excludes the Son from being true God, so here the phrase “God is One,” excludes Him from being God in any sense. But if, although the Father is called “One God,” the Son is nevertheless God, it is very plain that though the Father is called “Very God,” the Son is very God likewise. Now a mediator, says he, is between two parties; of whom then is Christ the Mediator? Plainly of God and of men. Observe, he says, that Christ also gave the Law; what therefore it was His to give, it is His to annul.
Ver. 21. “Is the Law then against the promises of God?”
For if the blessing is given in the seed of Abraham, but the Law brings in the curse, it must be contrary to the promises. This objection he meets, first, by a protest, in the words,
Ver. 21. “God forbid:”
And next he brings his proof;
Ver. 21. “For if there had been a law given which could make alive verily righteousness would have been of the Law.”
Source: Commentary on Galatians (New Advent)