Galatians 3:17–18

Law is excluded from this covenant of promise. It has absolutely no place there. The apostle's proof is this: God made and confirmed it four hundred and thirty years before the covenant at Sinai. Even a man's covenant, once made and confirmed, cannot be reopened to insert new conditions. How simply impossible, then, to add the law as a condition to the covenant of grace!

If a man offers a reward and attaches a condition to it, that is fair. But suppose you said to someone: I intend to leave you my house and garden, with no condition attached. Then, a year or two later, you said to him: You must pay me a thousand pounds for the house and garden. He might answer: What do you mean? Do you take back your promise? You gave me the property with no conditions, and now you ask me for payment! God's promise to Abraham was absolute, and it must always remain untouched.

God took care that, between the promise given to Abraham and Isaac and the law, there should pass a period of more than four centuries. Had He given the law a short time after, they might have said it was all one and the same thing. But how could anyone think that, seeing that four hundred and thirty years passed between? The promise has its own special object, and the law has its design too; and we are not to mix the two things together.

The promise to Abraham came long before Israel went into Egypt. The law came after they came out. So according to this passage, their stay in Egypt must have been much less than four hundred years.

God had bound Himself to Abraham by promise 430 years before the law, having placed, so to speak, the blessing of the Gentiles in him. This promise was confirmed to his seed, and to only one; he does not say to the seeds, but "to the Seed," and it is Christ who is this Seed. A Jew would not deny this last point. The law came long after. It could not annul the promise God had already made and solemnly confirmed, so as to make it of no effect.

Dishonest men have an old trick. They get a document they dislike thrown out by adding to it something that contradicts its main terms, so the whole thing falls apart. This is not allowed among men, and we must not think of God's covenant of promise as less sacred than human documents. The law, which was not given until 430 years afterwards, has not annulled it. And nothing has been added to it to change its blessed simplicity. It was never meant to do either of these things.

The law does not clash with the promise. Each has its own object: the law is a ministry of death and condemnation, the promise one of blessing by faith. Mixing the two is what does the harm. This is exactly what people are prone to, and what Scripture always clearly sets aside.

Moses was the servant of God through whom the law came. Yet he falls back, not on the law covenant — everything was lost on that basis — but on the unconditional covenant God made much earlier with Abraham, Isaac, and Israel. By an instinct given to him by God, Moses in his plea left law for grace. On that ground his plea succeeded.

If a man gets something because of what he has given or done for it, he does not have it by promise. He has what he earned. It is like a person doing so much work for so much pay. Of course, if a master gives his servant a present, the man is thankful for it. But when the pay only matches the work done, it is a debt, not a gift. The law is the principle of what is owed, if such a thing could be found among men. But all that man earned was a curse, because man was a sinner.

If the inheritance comes on one principle, says the apostle, then it does not come on the other. God gave it to Abraham and his seed by promise, and He cannot go back from that. And since we are in Christ, who is Abraham's seed, we are "heirs according to promise" (v. 29).

"The inheritance" means, I think, all that was included in the promises… The link with what goes before seems to be this. First, the law brings no blessing to those who stand on that ground; it brings a curse. Second, we inherit the blessing by promise, not by law. Christ receives that promise as the risen seed, the Second Adam. So it is open to the Gentile just as much as to the Jew, if he believes. For death and resurrection end every distinction and privilege of the flesh.

He does not stop here to show that righteousness by law is impossible for man. He insists instead that such a way of being justified, and of gaining the blessing by it, does not fit the plain terms of God's earlier covenant… But God gave the inheritance (kecharistai, "has freely given"), he says, when He promised it. Faith has what it believes, because it rests on the word of One who is almighty and cannot lie. So the very terms of law shut out the idea that we gain anything from God by law.

Here we have a covenant of gift, and the only party to it was God. He stooped to enter it, so that man might know how solemn and unchangeable His promise is… The law was conditional. Making the golden calf forfeited it, and that happened even before its conditions were declared. The law was also temporary. But the inheritance came by promise, and so it was secure. Why? Because it rested on God alone, who is one.

When God has something to give to man that can never fail, He loves to appear in grace and give it, or say it, Himself… With the law, two came in between: the angels and Moses the mediator. What a contrast with the simplicity of grace! In the law, man had to give. In the promise, man had only to receive.

Galatians says no more about the heir, and it mentions the inheritance only once (chapter 3:18). Yet these words seem to open the door of the Father's house and let us look in, and catch a glimpse of the glory that waits for us there… The time for the glory has not come yet. But we are heirs already, and in Christ we have already obtained an inheritance.