We have learned that those who are under the law are under a curse. This is because being under the law does not mean that one keeps the law; rather, it means that one does not keep it, and is therefore under condemnation. How can sinful men be delivered from this state of condemnation? And make no mistake—all have sinned in this way.
Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree: That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith. Brethren, I speak after the manner of men; Though it be but a man’s covenant, yet if it be confirmed, no man disannulleth, or addeth thereto. Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ. And this I say, that the covenant, that was confirmed before of God in Christ, the law, which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect. For if the inheritance be of the law, it is no more of promise: but God gave it to Abraham by promise
We are redeemed from this curse of ours because Christ became a curse in our stead. The Bible pronounces a curse upon everyone hanged on a tree, and Christ was in fact hanged on a tree (v. 13). He did this in order that the blessing of Abraham might come upon the Gentiles, that is, the promise of the Spirit through faith (v. 14). Using a human illustration, Paul says that even a man-made covenant is not altered after the fact (v. 15). Now the promise was made to Abraham and His seed, meaning Christ (v. 16). The Mosaic law came centuries after the promise (to the Gentiles) was confirmed in Christ (v. 17). The law, which came later, was therefore not the ordained instrument through which the promise was to be fulfilled (v. 18).
In this passage, Paul is insisting that the promise to Christ in Abraham was foundational, and that the law was added later, for supplementary reasons. The law was therefore an instrument that was subordinate to the promise. The promise was not subordinate to the law. Such theological contextualization is crucial—how we answer such questions will determine whether we be joyful Christians or pious prunes.
Let’s push it further back. Unfortunately, many Christians have gone back past Abraham, back to Adam, in order to advance their understanding of the “covenant of works” that God had with Adam. In this view, grace only comes in after the Fall. But note what this does to Paul’s argument here—it makes a hash of it. Paul has impressed upon us that we need to understand that the promise came 430 years before the law. And to this, many contemporary theologians reply “yes, but that the law in another form” was two thousand years before that. So the law has foundational priority after all. In their defense, this is done because they want us to be saved by the second Adam’s “works,” and so we must be lost by the failure of the first Adam to “work.” But this misconstrues (almost completely) the nature of grace. If the first Adam had not fallen, would he have rendered thanks to God for His grace? When the second Adam faithfully stood the test, did He not do so? “In the midst of the congregation will I praise thee” (Ps. 22:22)? For what?
So the promise was made to the seed, that is, to Christ, and so the fulfillment of the promise is available to the “seeds” of Abraham, that is, to everyone who has faith in Christ. Paul is not arguing from the grammar to Christ; he is arguing from Christ to the grammar. This glorious promise is only possible in Christ, and so therefore the seed in Genesis had to be referring to Him. Keep in mind the fact that the word seed can be either singular or plural.
Christ became a curse for us. The promise of blessing for the Gentiles was given to Abraham and to his seed. And yet, all Abraham’s natural seed had come under the condemnation of the law through not keeping it. So far were they from bringing covenant blessings to the sons of Adam, they were actually dragging Adamic disobedience into the line of Abraham. With their Judaic distortions, the life preserver became an anvil. This is why the seed of Abraham in the promise had to be talking about Christ—otherwise the promise could not be fulfilled at all. Jews and Gentiles, natural sons of Adam, were both under condemnation.
In order to be free one had to be a child of the promise. But one could not be a child of the promise without also being a child of the great transaction. Christ became a curse for us on the tree, so that in Him we might become the righteousness of God (2 Cor. 5:20). Christ takes our curse, and we take His blessing. We are cursed in Him, and we are blessed in Him. We are crucified in Him, and we are raised in Him.