One of the common assumptions about the law of Moses is that it is our tutor or schoolmaster. That is, the law leads us to Christ. For this reason, it remains useful to us. In Galatians 3, Paul explains the temporary nature of the law, and contrasts it with the promise to Abraham. The promise given to Abraham was by faith, and came prior to the law, by 430 years. But the natural question in the minds of the Galatians may be, “Why then the law?” If the law is inferior to promise and is temporary, why did God give it? Paul answers, “the law was our guardian until Christ came.” The word rendered guardian here in the ESV is translated as schoolmaster in the KJV. No doubt this translation led some to believe that the law was a teacher, one who in fact led us to Christ. But that translation is deficient, and masks something of Paul’s meaning. The word is paidagogos, (pedagogue.) In the ancient world, the pedagogue was one who had charge of the underage heir, and the responsibility to keep them out of trouble. But the pedagogue was not a kind teacher.
“These pedagogues had the bad image of being rude, rough, and good for no other business . . . the figure of the pedagogue is looked upon as a hard but necessary instrument in bringing a person to achieve and realize virtue.” “Their name, consequently, had a stigma attached to it.” If the law performs a function of training, or of leading one to Christ, why would Paul speak negatively about it, using the words “imprisoned” and “captive”? Louis Martyn likewise doubts Paul’s intention to present the law as our teacher. The law “is not a pedagogical guide, but an imprisoning warden,” he says, in that “six of the ten times Paul refers to humans being ‘under the power of’ the paidagogos, he identifies that enslaving power as the Law.” Moreover, if the law had such a teaching function, Paul would not have considered it limited to a certain time in history. Das puts it this way: “If the pedagogue were fulfilling a positive educational function in leading people to Christ, it would be unclear why Paul would consider the pedagogy to have ended with Christ’s coming.”
Paul says that the law was added because of transgressions. Does this mean it helps to control sin? Such a view is inconsistent with Paul’s other pronouncement on the purpose of law. In Romans 5:20, he is even more explicit. “the law came in to increase the trespass.” Given what the apostle says in both Romans and Galatians, we cannot say that the law is our tutor to lead us to Christ. While Paul always says the law is good, he also says that we are not. Our flesh never responds positively to it. The images of imprisonment and captivity that Paul uses in Galatians 3 reinforce the fact that the law was temporary in purpose, and only until Christ came. The law was not contrary to God’s purpose, but neither is it necessary now that Christ and faith in him have come. What the law teaches is the knowledge of sin. To walk worthily in Christ, the law is not our teacher. The spirit-enabled believer walks by faith, and as Paul has said at the earlier in the chapter, “The law is not of faith.”For a fuller discussion, see If One Uses It Lawfully: The Law of Moses and the Christian Life.
 Hans Dieter Betz, Galatians: A Commentary on Paul’s letter to the churches in Galatia (Philadelphia, Fortress Press, 1979), 177.
 Herman Ridderbos, The Epistle of Paul to the Churches of Galatia (Grand Rapids, Wm. B. Eerdmans, 1953), 146.
 J. Louis Martyn Galatians (New York, Doubleday, 1997), 363.
 A. Andrew Das, Galatians (St. Louis, Concordia Publishing House, 2014), 375.