This question, I believe, is significant. And answering it is not as easy as it might appear on first blush. What follows is certainly not the answer to this question, but a discussion on the matter, and offers at least in part what is my best answer at present. This is an area I find myself growing in regularly and my answer developing as the years go by. In this brief devotional, I am merely reflecting on thoughts I had this morning as I interacted with another answer to this question.
Hebrews 10:1 “The law is only a shadow of the good things that are coming—not the realities themselves. For this reason it can never, by the same sacrifices repeated endlessly year after year, make perfect those who draw near to worship.”
This is the simplest answer that I can find in Scripture. Of course, simple on the surface. Debating its meaning might be the work of many scholars. However, when I compare it to definitions which are commonly set forth or assumed, I think it is the simplicity of this statement that bears considering.
One English minister, writing in the late 16th century, defined law as “that which commands all good, and forbids all evil,” while the Gospel, “contains the free promises of God made unto us in Jesus Christ, without any respect of our deservings.”1 The truth he is trying to set forth regarding justification by works of the law vs. grace through faith I certainly embrace. However, this definition of Gospel and law might be a shortcut to the truth that confuses things a bit for me. By this definition, the law is not a shadow of the Gospel, but something that is the opposite of the Gospel. And since there are promises in the Old Testament, and “commands” to do good in the New Testament, we would be left to say that the Old Testament is full of Law and Gospel and the New Testament is full of Law and Gospel. Indeed, by this definition, Jesus taught both law and Gospel. Maybe.
However, if the concept of a shadow is taken a bit more seriously, we might think differently. If the Law is a shadow, then I should expect to find in it both command and promise. And then, in the Gospel, I might expect to find both command and promise, but with greater clarity, even more accuracy, than I found in the Law. By the shadow of something, I might be able to get an idea of what the real thing is. But when I have the real thing, I have greater clarity, more accurate details and specifics about what the shadow was revealing.
What's the difference? I think there are probably many. But as an example, I think we tend to miss some important truths by what I might call an over-simplification of the Law vs. Gospel. As a case in point, let's look at just one example: Galatians3:22-27, with particular emphasis on vs. 24.
But the Scripture declares that the whole world is a prisoner of sin, so that what was promised, being given through faith in Jesus Christ, might be given to those who believe. Before this faith came, we were held prisoners by the law, locked up until faith should be revealed. So the law was put in charge to lead us to Christ that we might be justified by faith. Now that faith has come, we are no longer under the supervision of the law. You are all sons of God through faith in Christ Jesus, for all of you who were baptized into Christ have clothed yourselves with Christ.
By the Greenham definition, we can say that the commands were put in charge to show us our sinfulness until grace was revealed in Christ that we might be justified by faith. And that is a wonderful truth. However, we stop short of what I think is a fuller meaning of the verses in question. If the Law is a shadow containing both command and promise, the same truth can be gained, because we know that the Law wasn't the final answer but a shadow waiting for fulfillment. But we can also discover other truths about the role of the Law as a guardian.
In addition to showing us our need for a Savior from our sin, the law taught us a whole new language and understanding of how God works. The law taught us about the need for sin to be paid for, the concept of substitution with animal sacrifices being used to cover sin rather than God just killing each sinner, the concept of God dwelling amongst us again in the tabernacle, the idea of God's wrath and the satisfaction of that wrath. And many of these things were found in the promises of the Law and the provisions of grace in the law. In fact, without the Law, we could never have recognized Jesus Christ to be the Savior. John's Gospel speaks of the inconsistency of the leaders of the Jews, who studied the law, but not recognizing Jesus. They missed the whole point of the Law—to lead to Christ that they might have life. And the means by which they were to come to Christ was that they should have recognized Him. The shadow should have made the Reality recognizable.
There are other implications and distinctions that could be made and maybe they will be the topic of a future devotion.
Love the Gospel, Live the Gospel, Advance the Gospel,
1Richard Greenham; language updated. Quoted in Calvin and English Calvinism to 1649. This is not the first writer I've run across that communicates this. In fact, this would be a commonly held view.