If you really fulfill the royal law according to the Scripture, "You shall love your neighbor as yourself," you do well; James 2:8NKJ
Question 97 of the Larger Catechism, asks, "What special use is there of the moral law to the regenerate?" It gives the answer, "Although they that are regenerate, and believe in Christ, be delivered from the moral law as a covenant of works, so as thereby they are neither justified nor condemned; yet, besides the general uses thereof common to them with all men, it is of special use, to show them how much they are bound to Christ for his fulfilling it, and enduring the curse thereof in their stead, and for their good; and thereby to provoke them to more thankfulness, and to express the same in their greater care to conform themselves thereunto as the rule of their obedience." We have already looked at how the moral law is of use to all men (Q. 95), and exclusively to unregenerate men (Q. 96). Last time we saw that Christ did not justify us in a Covenant of Works but in the Covenant of Grace. This week we consider how God's law is useful to people who already believe in Jesus Christ as their Lord and Savior.
First, the moral law shows believers how much we are bound to Christ for fulfilling its demands and for suffering its curse in our stead. When we look at the moral law and see how it requires perfect and perpetual obedience (James 2:10); and when we see how God will not compromise that demand for anyone or for any reason (Exod. 23:7; Acts 10:34-35); then we know and feel just how much we need to be in union with Christ. Here, the law does not drive the unconverted sinner to Christ, but its use by the converted believer should help to keep him close to Christ. The law shows me that even my best works as a redeemed child of God need to come through the blood of Christ or they cannot be accepted by God. Knowing this fact, I will want to keep close to Christ in order to acceptably serve Him. Likewise, when I see from the law, how Christ satisfied the curse of the Covenant of Works for me, I will be reminded that all of my blessedness comes from being in union with Christ. This knowledge should provoke me to be more thankful to Jesus, and more zealous, therefore, to do the good works that please Him.
Here, someone will ask, "But how do I know what pleases God?" You know what pleases God by the moral law, because in the moral law God has commanded those creatures made in His image to do those things that please Him. Calvin is justly renowned for his famous "third use of the law." According to Calvin, the third use of the law is exclusively for believers as it shows them how to please their God:
The third use of the Law (being also the principal use, and more closely connected with its proper end) has respect to believers…. For it is the best instrument for enabling them daily to learn with greater truth and certainty what that will of the Lord is which they aspire to follow, and to confirm them in this knowledge…. The servant of God will derive this further advantage from the Law: by frequently meditating upon it, he will be excited to obedience and confirmed in it, and so drawn away from the slippery paths of sin…. The object of the Psalmist [in Psalm 119] is to celebrate the advantages which the Lord, by means of his law, bestows on those whom he inwardly inspires with a love of obedience, (Institutes 2.7.12).
Notice, Calvin calls this use of the law its "principal use," as it is "more closely connected with its proper end." What Calvin means is that God's law only condemns sinners "accidentally." That is, the law, being a reflection of the righteous character of God, is the standard of perfect goodness. That is all it does inherently: it shows us what goodness is. However, when a person sins against the law, now that sinner is condemned by that perfect law. The ultimate cause of that condemnation is not the law, but the sin. Accordingly, Calvin calls the law "the best instrument for enabling" believers to know how to please God. Furthermore, when believers study the law they will be "excited to obedience." How could they not be? The law shows them what God is like, and therefore, those who love God will love His law and they will want to do it! Take some time today to read Psalm 119, and praise God for His beautiful law!