When one reads the New Testament, and in particular Paul’s epistles, one can’t help see how the law of Moses is a prominent theme in the apostle’s thought. How he treats it is of great importance to how Christians should regard it. First, one has to say that for Paul, “the Law” is specifically those commandments given at Sinai, and following. The holiness code of Leviticus 18-22 is also part of the law, and an overarching truth for Paul is summarized in Rom. 3:19: “Now we know that whatever the law says it speaks to those who are under the law.” In other words, Paul refers to the Jewish nation. To them alone were the laws of the Mosaic covenant given. Paul earlier in Romans spoke of Gentiles who “do not have the law.” (Rom. 2:14). It is true that Gentiles sometimes act according to what the law requires, but Paul is careful to point out that they do this by nature or conscience, “even though they do not have the law” and not be revelation.
How then does Paul regard this law with respect to Christians? For everyone within the Protestant category, all would say that justification comes by faith apart from doing any of the law. But some retain a use for the law as a guide to know how to live, what God requires of us, how to please God. This, in brief, is the “Third Use of the law.” John Calvin expounded this quite clearly, and later confessional standards took it up as well. Calvin said, “The third and principal use of the law, which pertains more closely to the proper use of the law, finds its place among believers in whose hearts the Spirit of God already lives and reigns.” He continued, “however eagerly they may in accordance with the Spirit strive toward God’s righteousness, the listless flesh always so burdens them that they do not proceed with due readiness. The law is to the flesh like a whip to an idle and balky ass, to arouse it to work.”
Against this view is another that sees the Law less as a standard we must adhere to, and more as wisdom and prophecy that informs and complements the specific instructions of the apostle’s themselves. Brian Rosner of Ridley Melbourne Mission and Ministry College in Australia ably expounds this in his book Paul and the Law: Keeping the Commandments of God. Rosner notes among other things how Paul repudiates the law as a covenant in any way binding upon believers.
“Unlike Jews, believers in Christ are not under the law, nor are they in the law or from the law. They are not imprisoned and guarded under the law, nor are they subject to the law as to a disciplinarian. Those who are under the law are under a curse and under sin. Even though the law promises life to those who keep it, it is evident that no one keeps the law. Consequently, no one receives life through the law. The law used as law is for the lawless. Christ has abolished the law with its commandments and ordinances.”
He notes that any covenantal aspect of the law is for Jews only. A covenant is a binding treaty, and thus comes with obligation. Indeed, one can scarcely read the Pentateuch without seeing God’s repeated warnings to be careful to keep the entirety of the law.“You shall therefore be careful to do the commandment and the statutes and the rules that I command you today.” (Deut 7:11) Such an obligation does not belong to Christians now, because we are not under the Mosaic covenant, nor part of Jacob’s seed.
The other point Rosner makes is that although we are not under the law as a covenant, this does not mean there is no value in it at all. It is in “wisdom and prophecy” where the value comes to believers. This sometimes comes in surprising applications. Paul, for example, cites the commandment to not muzzle an ox as it treads out the grain (Deut. 25:4) as a reason why ministers of the gospel who labor full time in the Word should be paid for this work—a rather unexpected application of this law, to be sure.
Even in the sections where Paul seems to directly cite the commandments, such as Romans 13:9-10, which contains commandments 6,7,8, and 10, Paul doesn’t in fact say “You must keep these commandments.” Rosner notes
“Paul’s point is that loving one’s neighbour is the goal of keeping the law. But keeping the laws (even those of the Decalogue, such as laws against adultery, murder, stealing and coveting) does not mean that one will love one’s neighbour. But if one loves one’s neighbour, one will do more than just keep the law, fulfilling what Paul takes to be its real intent.”
What Rosner outlines is where I believe the Third Use digresses. That is, Calvin had assigned to the law abilities that Paul explicitly rejects, namely, the ability to call forth obedience in the believer. (“The law is to the flesh like a whip to an idle and balky ass, to arouse it to work.”) Paul says instead that the law arouses sin (Rom 7:5), and was given to increase the trespass. (Rom 5:20) But, doesn’t Calvin qualify his counsel to say that the law “finds its place among believers in whose hearts the Spirit of God already lives and reigns.”? Indeed, Calvin does, but is this what Paul teaches? Paul has set the Spirt and the law in opposition to one another, not because the law is bad, but because it belongs to a prior covenant, to a different people, and to those not under the headship of Christ. Paul told the Galatians that the law is not of faith. No such thing as a faith-enabled keeping of the law is anywhere in Paul’s teaching.
To the extent that the Third Use of the law presents Christians obeying or keeping the law through the enablement of the Holy Spirit, it strays from the apostolic use of the law. Paul’s avowal that we have died to the law in order to live to another rules this out. Indeed, in Galatians 5:18 he notes “But if you are led by the Spirit, you are not under the law.” To follow the Spirit’s leading and guidance in our lives does not lead us to “keep the law” —though indeed we fulfill the law’s intent of loving one another. To distinguish between keeping and fulfilling is in essence the difference between the Third Use and the Law as wisdom.
If advocates of the Third Use agree that Paul repudiates any obligation to the law for Christians, that he instead uses it as wisdom, but a kind of lowest common denominator of what we are called to, that would be a different matter. Indeed, the law’s commandments are not in conflict with the holiness God now calls us to, but they in fact don’t go far enough. As Rosner pointed out, just “keeping” them does not mean I love. I have most often encountered a view that presents the law (and only the Ten Commandments) as not only a required standard for Christians, but indeed, a revelation of God’s mind and will for Christians. That does not accord with the multiple ways Paul presents the law in his epistles. The topic is a complex issue, to be sure. For further discussion, please see my book, If One Uses It Lawfully: The Law of Moses and the Christian Life. (Wipf and Stock, 2018).
 Calvin, Institutes of the Christian Religion, 2.7.12.
 Calvin, loc. Cit.
 Brian S. Rosner, Paul and the Law: Keeping the Commandments of God (Downers Grove, InterVarsity Press, 2013), 221.
 Rosner, 193.