Today we pick up our study in Galatians 3:19 which says, “Wherefore then serveth the law? It was added because of transgressions, till the seed should come to whom the promise was made; and it was ordained by angels in the hand of a mediator.” So, the question now is, “If the Law did not set aside or even add to the promise that God made to Abraham what was the purpose of giving it at all?” It was added because of transgressions. Sin! Romans 4:15 says, “Because the law worketh wrath: for where no law is, there is no transgression.” Also, Romans 5:20 says, “Moreover the law entered, that the offence might abound. But where sin abounded, grace did much more abound:” So, the Law was to point out our falleness until the Messiah would come and offer a way to fix it. Romans 10:4 says, “For Christ is the end of the law for righteousness to every one that believeth.”
An evangelist by the name of Fred Brown used three images to describe the purpose of the law. First he likened it to a dentist's little mirror, which he sticks into the patient's mouth. With the mirror he can detect any cavities. But he doesn't drill with it or use it to pull teeth. It can show him the decayed area or other abnormality, but it can't provide the solution.
Brown then drew another analogy. He said that the law is also like a flashlight. If suddenly at night the lights go out, you use it to guide you down the darkened basement stairs to the electrical box. When you point it toward the fuses, it helps you see the one that is burned out. But after you've removed the bad fuse and inserted a new one, you turn off the flashlight as that it is no longer needed.
In his third image, Brown likened the law to a plumb line. When a builder wants to check his work, he uses a weighted string to see if it's true to the vertical. But if he finds that he has made a mistake, he doesn't use the plumb line to correct it. He gets out his hammer and saw. The law points out the problem of sin; it doesn't provide a solution. Of course, the mediator spoke of in this verse is referring to Moses.