The interpretation timeline
Galatians 2:21 Douay-Rheims

I cast not away the grace of God. For if justice be by the law, then Christ died in vain.

A.D. 407 – 1871 6 witnesses

Patristic

before A.D. 750
407
A.D.
John Chrysostom Patristic
A.D. 347–407
“"I do not make void the grace of God." Let those, who even now Judaize and adhere to the Law, listen to this, for it applies to them. "For if righteousness is through the Law, then Christ died for naught." What can be more heinous than this sin? what more fit to put one to shame than these words? Christ's death is a plain proof of the inability of the Law to justify us; and if it does justify, then is His death superfluous. Yet how could it be reasonable to say that has been done heedlessly and in vain which is so awful, so surpassing human reason, a mystery so ineffable, with which Patriarchs travailed, which Prophets foretold, which Angels gazed on with consternation, which all men confess as the summit of the Divine tenderness? Reflecting how utterly out of place it would be if they should say that so great and high a deed had been done superfluously, (for this is what their conduct came to,) he even uses violent language against them, as we find in the words which follow.”
Source
749
A.D.
John of Damascus Patristic
A.D. 676–749
“I have been freed through the grace, he says. Therefore, I do not turn back to the Law, nor do I revile the grace as being impotent to vivify. "For if righteousness is through the Law, the Christ has died in vain." Christ died for us, he says, that he might raise us up, justifying us and removing sin from our midst. But if those who attempt to persuade others to be circumcised say that man is justified in the law, then the death of Christ is made redundant.”
Source

Scholastic

c. 1100 – 1500
1273
A.D.
Thomas Aquinas Catholic
1225–1274
“Here the Apostle manifests the solution assigned above. And first he sets forth the manifestation of the solution; second he concludes his principal intention, at the words "I do not cast away the grace of God," etc. But it must be noted that the Apostle, proceeding by way of inquiry, leaves no doubt undiscussed. And therefore, although his words may seem intricate, nevertheless if they are carefully attended to, he says nothing without a reason, and this is apparent in the words proposed. Here he does three things: first he manifests the solution; second he explains the manifestation of the solution, at the words "I am fixed to the cross with Christ," etc.; third he removes a doubt, at the words "and that I now live," etc. Since, then, the Apostle had said, "for if the things I have destroyed," etc., which is understood of the old Law — for he could be reckoned by someone a destroyer of the Law, and consequently unjust, according to that word of Psalm 118:126: "The wicked have destroyed thy law" — the Apostle therefore wishes to show how he destroys the Law, and yet is not unjust, saying, "for I through the Law," etc. Here it must be known that when someone dissolves the law through the law itself, such a one is a transgressor of the law, not an unjust man. But the law is dissolved through the law when in the law some local or temporal precept is given — namely, that that law be observed at such a time, or in such a place, and not another, and this itself is expressed in the law. If someone then does not make use of the law at that time, or in that place, he destroys the law through the law itself, and in this way the Apostle destroyed the law. Hence, he says, I destroyed the law in a certain way, yet through the law, because I have died to the law through the law — that is, through the authority of the law I let it go, as one dead to the law. For the authority of the law, by which he died to the law, is found in many places of sacred Scripture: Jeremiah 31:31, though under other words: "I will confirm a new covenant upon the house of Israel," etc.; Deuteronomy 18:15: "The Lord will raise up a prophet from among your brethren," etc.; and in many other places. Therefore the Apostle is not a transgressor in destroying the law. Or otherwise: I, through the law — namely, the spiritual law — have died to the carnal law. For then does one die to the law, when, released from the law, he casts it off, according to that word of Romans 7:2: "The husband being dead, the woman is loosed from the law of the husband." Insofar as the Apostle was subject to the spiritual law, he says that he is dead to the law — that is, released from the observance of the law. Romans 8:2: "The law of the spirit of life," etc. There can be another way of letting go of the law without transgression, namely because when some law is written on paper, it is then called a dead law, and when it is in the mind of the lawgiver, it is then called a living law. Now it is clear that if someone were to act, according to the word of the lawgiver, against the written law, he would both dissolve the law and be released from the dead law, and would keep the living law according to the command of the lawgiver. According to this, then, he says: I have died to the law that is written and dead — that is, I am released from it — that I may live to God, that is, that I may direct my movements according to his own sayings, and be ordered to his honor. For the law established in writings hands something down on account of strangers, and those who cannot hear it word for word from him; but to those who are in his presence, he does not state it in writings, but by word alone. For from the beginning men were weak, unable to approach God. And therefore it was necessary to give them the precepts of the law in writings, so that through the law, as through a tutor, they might be led by the hand to this — that they might hear his precepts from him — according to what is said below, chapter 3:24: "The law was our tutor in Christ," etc. But after we have access to the Father through Christ, as is said in Romans 5:2, we are not instructed about the commandments of God through the law, but by God himself. And therefore he says: through the law that leads by the hand, I have died to the written law, that I may live to God — namely, to the very maker of the law — that is, that I may be instructed and directed by him. Next, when he says "I am fixed to the cross with Christ," etc., he explains what he has said. For he had said that he is dead to the law, and that he lives to God. And these two things he manifests. And first, that he is dead to the law, by what he says: "I am fixed to the cross with Christ"; second, that he lives to God, when he says "I live, now not I," etc. And the first indeed can be expounded in two ways. In one way, as in the Gloss, thus: every man according to his carnal origin is born a son of wrath, Ephesians 2:3: "For we were by nature children of wrath," etc. He is also born in the oldness of sin, Baruch 3:11: "Thou hast grown old in a strange land," etc. This oldness of sin indeed is taken away through the cross of Christ, and the newness of spiritual life is conferred. The Apostle therefore says, "I am fixed to the cross with Christ," that is, concupiscence, or the kindling-wood of sin, and everything of this sort, has died in me through the cross of Christ. Romans 6:6: "Our old man is crucified together with him," etc. Likewise, since I am fixed to the cross with Christ, and have died to sin, and Christ rose again, I too have risen together with him who rose. Romans 4:25: "He was delivered up," etc. Thus, then, Christ renews a new life in us, the oldness of sin having been destroyed. And therefore he says "but I live" — that is, because I am fixed to the cross with Christ, I have the vigor of acting well — "now not I" according to the flesh, because I no longer have the oldness which I had before, "but Christ lives in me," that is, the newness which has been given to us through Christ. Or otherwise: a man is said to live with respect to that in which he principally fixes his affection, and in which he takes the greatest delight. Hence also men who take the greatest delight in study or in hunting say that this is their life. Now every man has a certain private affection, by which he seeks what is his own; therefore while someone lives seeking only what is his own, he lives to himself alone, but when he seeks the goods of others, he is said to live to them also. Since, then, the Apostle had laid aside his own affection through the cross of Christ, he was saying that he was dead to his own affection, saying "I am fixed to the cross with Christ" — that is, through the cross of Christ my own or private affection has been removed from me. Hence he was saying below, at the end: "Far be it from me to glory save in the cross of our Lord," etc.; 2 Corinthians 5:14f.: "If one died for all, then all died." And Christ died for all, that they also who live may now live not to themselves, but to him, etc. "But I live" — that is, "now I do not live," as it were having my own good in my affection, "but Christ lives in me," that is, I have only Christ in my affection, and Christ himself is my life. Philippians 1:21: "To me to live is Christ, and to die is gain." Next, however, when he says "and that I now live," etc., he responds to a doubt which could be twofold from the word set forth above. One is how he himself lives, and yet is not the one — namely, who lives; the second is how he is fixed to the cross. And therefore he opens up these two things. And first the first, namely how he lives, and yet he himself does not live, saying "and that I now live," etc. Here it must be noted that those things are properly said to live which are moved from an intrinsic principle. Now the soul of Paul was set between God and the body, and the body indeed was vivified and moved by the soul of Paul, but his soul by Christ. As to the life of the flesh, then, Paul himself lived, and this is what he says: "and that I now live in the flesh" — that is, the life of the flesh; but as to relation to God, Christ was living in Paul, and therefore he says "I live in the faith of the Son of God," through which he dwells in me and moves me. Habakkuk 2:4: "But my just man lives by faith." And note that he says "in the flesh," not "from the flesh," because this would be evil. Second, he shows that he is fixed to the cross, saying: because the love of Christ, which he showed to me on the cross, dying for me, causes me always to be fixed to him. And this is what he says: "who loved me." 1 John 4:10: "He first loved us." And he loved me to such an extent that he delivered himself up for me, and no other sacrifice. Apocalypse 1:5: "He loved us, and washed us from our sins in his own blood." Ephesians 5:25: "As Christ also loved the Church, and delivered himself up for her," etc. But it must be noted that the Son himself delivered himself up, and the Father delivered up the Son, Romans 8:32: "Who spared not even his own Son, but delivered him up for us all"; and Judas delivered him up, as is said in Matthew 26:48. And it is all one and the same deed, but not one and the same intention, because the Father acted out of charity, the Son out of obedience together with charity, but Judas out of cupidity and treacherously. Next, when he says "I do not cast away the grace of God," he infers the principal conclusion. And first he brings forth the conclusion; second he manifests the manner. He says therefore: since I have received so great a grace from God, that he delivered himself up, and I live in the faith of the Son of God, I do not cast away the grace of the Son of God — that is, I do not repudiate it, nor do I show myself ungrateful. 1 Corinthians 15:10: "The grace of God in me has not been void," etc. Hence another text also has: "I am not ungrateful to the grace of God" (Hebrews 12:15: "looking diligently lest any man be wanting to the grace of God"), namely by confessing oneself unworthy through ingratitude. Now the manner of casting away and of ingratitude would be, if I were to say that the law was necessary for justifying. And therefore he says: "for if justice be by the law, then Christ died in vain" — that is, if the law is sufficient, that is, if the works of the law suffice to justify man, Christ died without cause, and in vain, because he died for this purpose, that he might justify us. 1 Peter 3:18: "Christ died once for our sins," etc. But if this could be done through the law, the death of Christ would have been superfluous. But he did not die in vain, nor did he labor in vain, as is said in Isaiah 49:4, because through him alone justifying grace and truth came to be, as is said in John 1:17. If any were just before the passion of Christ, this too was through faith in Christ who was to come, in whom they believed, and in whose faith they were saved.”

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“I do not frustrate the grace of God,.... Or "cast it away", as the Vulgate Latin version reads it; or "deny it", as the Syriac and Arabic; or "despise, reject, and make it void", as other versions; meaning either the grace of the Son of God in giving himself for him, just mentioned by him; or the particular doctrine of grace, justification, he is speaking of, as proceeding from the grace of God, upon the foot of the righteousness of Christ; or the whole Gospel, all and each of which would be denied, despised, rejected, made null and void, be in vain, fallen and departed from, should justification be sought for by the works of the law: but this the apostle did not do, and therefore did not frustrate the grace of God: which to do would be to act the most ungenerous and ungrateful part to God, and Christ, and to that love and grace which are so largely displayed in the free justification of a sinner. For if righteousness come by the law; if a justifying righteousness is to be attained unto by the works of the law, or men can be justified by their obedience to it, then Christ is dead in vain; there was no necessity for his dying: he died without any true reason, or just cause; he died to bring in a righteousness which might have been brought in without his death, and so his blood and life might have been spared, his sufferings and death being entirely unnecessary; which to say is to cast contempt upon the wisdom, love, and grace of God in this matter, and to offer the greatest indignity to the person, character, sufferings, and death of Christ. Wherefore it may be strongly concluded, that there is no righteousness by the law of works, nor to be attained that way, otherwise Christ had never died; and that justification is solely and alone by his righteousness. Next: Galatians Chapter 3”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“I do not frustrate - Ουκ αθετω· I do not contemn, despise, or render useless, the grace of God - the doctrine of Christ crucified; which I must do if I preach the necessity of observing the law. For if righteousness - If justification and salvation come by an observance of the law, then Christ is dead in vain; his death is useless if an observance of the law can save us; but no observance of the law can save us, and therefore there was an absolute necessity for the death of Christ. 1. The account of the prevarication of Peter in the preceding chapter teaches us a most useful lesson. Let him who assuredly standeth take heed lest he fall. No person in a state of probation is infallible; a man may fall into sin every moment; and he will, if he do not walk with God. Worldly prudence and fleshly wisdom would have concealed this account of the prevarication of Peter; but God tells truth. This the fountain of it; and from him we are to expect not only nothing but the truth, but also the whole truth. If the Gospel were not of God we had never heard of the denial and prevarication of Peter, nor of the contention between Paul and Barnabas. And these accounts are recorded, not that men may justify or excuse their own delinquencies by them, but that they may avoid them; for he must be inexcusable who, with these histories before his eyes, ever denies his Master, or acts the part of a hypocrite. Had the apostles acted in concert to impose a forgery on the world as a Divine revelation, the imposture would have now come out. The falling out of the parties would have led to a discovery of the cheat. This relation, therefore, is an additional evidence of the truth of the Gospel. 2. On, I through the law am dead to the law, etc., pious Quesnel makes the following useful reflections: "The ceremonial law, which is no more than a type and shadow of him, destroys itself by showing us Jesus Christ, who is the truth and the substance. The moral law, by leaving us under our own inability under sin and the curse, makes us perceive the necessity of the law of the heart, and of a Savior to give it. The law is for the old man, as to its terrible and servile part; and it was crucified and died with Christ upon the cross as well as the old man. The new man, and the new law, require a new sacrifice. What need has he of other sacrifices who has Jesus Christ? They in whom this sacrifice lives, do themselves live to God alone; but none can live to him except by faith; and this life of faith consists in dying with Christ to the things of the present world, and in expecting, as co-heirs with him, the blessings of the eternal world. And who can work all this in us but only he who lives in us? That man has arrived to a high degree of mortification, who can say Christ liveth in me, and I am crucified to the world. Such a one must have renounced not only earthly things, but his own self also." 3. Is there, or can there be, any well grounded hope of eternal life but what comes through the Gospel? In vain has the ingenuity of man tortured itself for more than 5000 years, to find out some method of mending the human heart: none has been discovered that even promised any thing likely to be effectual. The Gospel of Christ not only mends but completely cures and new makes infected nature. Who is duly apprised of the infinite excellency and importance of the Gospel? What was the world before its appearance? What would it be were this light extinguished? Blessed Lord! let neither infidelity nor false doctrine rise up to obscure this heavenly splendor!”
Source
1871
A.D.
1871
“I do not frustrate the grace of God--I do not make it void, as thou, Peter, art doing by Judaizing. for--justifying the strong expression "frustrate," or "make void." is dead in vain--Greek, "Christ died needlessly," or "without just cause." Christ's having died, shows that the law has no power to justify us; for if the law can justify or make us righteous, the death of Christ is superfluous [CHRYSOSTOM]. Next: Galatians Chapter 3”
Source
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.