The second commandment centers on worship. “You shall not make for yourself an idol, or any likeness of what is in heaven above or on the earth beneath or in the water under the earth. You shall not worship them or serve them” (Ex. 20:4-5). The Westminster Shorter Catechism (51) says, “The second commandment forbiddeth the worshipping of God by images, or any other way not appointed in his word” (italics added). This is a statement of the regulative principle of worship. We are not to worship in any way God does not command in His Word.

A noted professor of New Testament interpretation, arguing against exclusive psalmody, maintains, “The regulative principle of worship finds its final, decisive expression when Christ fulfills the law of Moses and the ordinances of David with superabundant fulfillment and riches” (Westminster Theological Journal 37/1 [Fall 1974], 82-83). He further states that the fulfillment of the regulative principle “is of a piece with the fulfillment of the priestly, kingly, and prophetic ministry” of the Old Testament: “All is fulfilled in Christ.”

Our brother’s argument mixes apples and oranges. As indicated above, the regulative principle arises from the second commandment. It is part of the moral law, which is perpetual. The Old Testament prophets, priests, and kings were prophetic types pointing forward to Christ and fulfilled in Him. They served under the ceremonial and civil law of Israel, which was temporary. Our professor friend also uses the term fulfilled in different ways. The prophetic types of prophet, priest, and king are fulfilled when Jesus Christ, the antitype, appears on the scene. Old Testament ceremonies are fulfilled when Christ fills out their meaning and sets them aside to establish His own sacrificial work as final (Heb. 10:9). Christ fulfills the moral law in a different way. He obeys it. Since the regulative principle is part of the moral law and therefore perpetual, it remains in force. God also calls us to obey it.

Our brother goes on to rightly say, “In our worship we are to strive for complete conformity to the law, bending all our efforts and finding all our joy in fulfilling it (not going beyond it with inventions).” Amen! However, the professor also says, “Moreover, it is conformity which is internal.” Expressing the need for this internal conformity, he continues, “We must have the mind of Christ.” How true. What happens when we fail? “We must see that Christ himself is the definitive embodiment of true righteousness.” Christ therefore fulfills the regulative principle: “All is fulfilled in Christ.” There is an ambiguity in his points.

Conformity to God’s moral law is not only internal. We must outwardly act according to God’s law. This includes the regulative principle. Yes, we must have the mind of Christ. John Calvin, following Athanasius, leads us in this direction in his preface to the Commentary on the Psalms, “[T]here is not an emotion of which any one can be conscious that is not here represented.” Athanasius teaches that “each one sings the Psalms as though they had been written for his special benefit” and we sing them “as a pattern and model for the amendment of our lives” (Letter of Athanasius to Marcellinus Concerning the Psalms). The Psalms are a divine guide for the expression of our thoughts and emotions in worship, and through them we also obey God in worship with our actions.

The lesson? The regulative principle remains in force. Psalmody helps us fulfill, follow, and obey it. As we sing the psalms in worship, God works internal conformity to His law in us by training our thoughts and emotions.