Toward the end of the Sermon on the Mount, Jesus said:
So whatever you wish that others would do to you, do also to them, for this is the law and the prophets. (Matthew 7:12)
I love that. The entire Old Testament is summed up in a single principle, and the principle is exciting: be radical and proactive and energetic in doing good to others — that is, treat others as you treat yourself, and how you would want them to treat you.
But, there’s a problem: Where’s the gospel?
This wouldn’t be a problem if Jesus just said “do unto others as you would have them do unto you.” The problem arises from the fact that he said this is the law and the prophets.
Didn’t Jesus also say “that everything written about me in the Law of Moses and the Prophets and the Psalms must be fulfilled” (Luke 24:44) and that they foretold not only his suffering and resurrection, but “that repentance and forgiveness of sins should be proclaimed in his name to all nations” (Luke 24:47)? The clear implication here is that the point, the essence, of the Old Testament is Jesus. Everything in the Scriptures points to Christ and is about him.
So, which is it? Are the law and prophets summed up as “do unto others as you would have them do unto you,” or are they summed up as “repent and believe in the death and resurrection of Christ for the forgiveness of sins”?
It’s both, with the later — Christ — having supremacy.
In other words, even the command to “do unto others as you would have them do unto you,” which sums up the Old Testament, points to Christ.
Because we all break it.
The point of the Old Testament in teaching the Golden Rule was not simply, or even mainly, to point the way to right behavior. It was first of all to say: “Look, you don’t live this way. None of you. And that’s a big deal. Israel went into exile for this. So you need a savior. You need to be rescued from your sins, from your hypocrisy in treating others the way you precisely would not want to be treated if you were in their position.”
And the rescue from our sins is Christ.
The Old Testament, in other words, points to Christ not only through symbols and types and prophecies of his coming, but also through indicting us of our sin and showing our need for him. It shows us the problem (our sin and consequent separation from God ) and the solution (faith in Christ and our consequent fellowship with him).
And then, having been justified in Christ apart from works (for we don’t have any), then we go forth eagerly and enthusiastically doing unto others as we would have them do unto us.
We still fail much, but we are now improving and growing and doing it without, at least all of the time or to the same extent, committing the greatest sin of all: ignoring Christ in our doing of good.
Here’s the best way I’ve ever heard it said: The law drives us to the gospel, and the gospel then frees us to obey the law. That’s the meaning of Matthew 7:12 (the Golden rule) and Luke 24:44-47 (a form of the Great Commission).
Or, in other words, that’s the meaning of the whole Bible.