One of the key insights recovered in the Reformation was the distinction between law and gospel in our justification. The law of God, the Reformers held, tells us what to do but does not give us the power to fulfill its commands. Thus, it ends up revealing our sin and our impotence. When we read or hear the law, we see how far short we fall of God’s standard and despair of our ability to be righteous in God’s sight. Then, we read or hear the gospel and its call to rest in Christ and receive His righteousness (Rom. 4), which alone can avail before God’s judgment. With the gospel comes God’s gift of faith for the elect; He enables us to believe and be justified (Eph. 2:8–10).
That distinction between law and gospel in our justification is one of the ways that the Reformers summarized the use of the law as a revealer of sin. Although the law does more than reveal our sin, for it also restrains sin and guides our sanctification, the law’s use in showing us our transgression is indispensable for our salvation. We cannot know that we need Christ unless we first get a glimpse of how bad off we are as sinners under the wrath of God.
God’s law, then, brings us to Christ, and Paul teaches us this explicitly when he refers to the law as our “guardian” (Gal. 3:24). The English word “guardian” translates the Greek term paidag gos, and the paidag gos served an important role in ancient education. A family appointed a guardian to supervise a child from about age six through the teenage years. The guardian took the child to his lessons, disciplined the child when he went astray, and reviewed school lessons with the child. In similar manner, the law, by teaching us our sin and warning us of judgment, is what brings us to Christ, from whom we receive the words of eternal life (John 6:68). Martin Luther writes in his commentary on Galatians, “The Law is a specialist to bring us to Christ.”
Of course, the law does not serve as the guardian that leads us to Christ only by revealing our sin. We also find in the law types and shadows of the atonement in the sacrificial system. In such a way, the law engendered hope in the old covenant saints for a mediator who would deal with sin once for all. Through its moral statutes, its sacrifices, and its ceremonial regulations, the law points to Jesus as the only Savior. John Calvin comments, “The law, in short, was nothing else than an immense variety of exercises, in which the worshippers were led by the hand to Christ.”