God does not tell us to worship at 9 am or 10 am. He does not tell us how many songs we should sing in a service. He does not tell us how often we should celebrate the Lord’s Supper. He does not tell us every prayer we should pray or which instruments to use or when to sit and stand in the service. These things require wisdom and the application of biblical principles. So we distinguish between the elements (which are commanded) and the circumstances (which require wisdom and reason).

The Second Commandment in its narrow sense prohibits the worship of images themselves—“You shall not make for yourself an idol [lit. ‘carved image’]… You shall not worship them or serve them” (Exodus 20:5, NASB95). By extension, the Reformed have held this to mean we should not use images in worship or to aid in worship in any way, though many Christian traditions disagree (especially Catholics and Orthodox).

However, in its broad sense, the Second Commandment regulates the entirety of how we worship God. It prohibits us form worshipping God in a way not prescribed in His Word. Stated positively, we should only worship God the way He has set down for us in His Word. This principle is known as the Regulative Principle of Worship (RPW). The RPW is seen in Westminster Confession of Faith 21.1, which says,

the acceptable way of worshiping the true God is instituted by himself, and so limited by his own revealed will, that he may not be worshiped according to the imaginations and devices of men, or the suggestions of Satan, under any visible representation, or any other way not prescribed in the Holy Scripture.

The RPW is also set forth in Westminster Shorter Catechism 50 and 51 on the Second Commandment. WSC 50 says, “The second commandment requireth the receiving, observing, and keeping pure and entire, all such religious worship and ordinances as God hath appointed in his word.” WSC 51 adds, “The second commandment forbiddeth the worshiping of God by images, or any other way not appointed in his word.”

So it is both: (1) We must practice that which God has set down in His Word regarding worship, (2) and we must not worship God in any way He has not set down. 

Deuteronomy 12 and the Second Commandment

This point is made in Deuteronomy 12, a chapter that covers the Second Commandment in Moses’ final sermon to Israel before they crossed the Jordan River into Canaan. After restating the Ten Commandments in Deuteronomy 5, Moses gave commands falling under each of the Ten Commandments in chapters 6–26. Deuteronomy 6–11 covers the First Commandment, urging Israel to give undivided loyalty to the Lord. Then Deuteronomy 12 follows by giving laws regarding the Second Commandment. What this means is Deuteronomy 12 contains a God-inspired exposition and application of the Second Commandment. It is the exposition of Moses himself, breathed out by the Spirit of God.

In Deuteronomy 12, Moses instructed Israel regarding worship as they entered the Promised Land of Canaan. He told Israel to destroy the all the places of Canaanite false worship—including tearing down altars, burning Asherim poles, and cutting down engraved images (Deuteronomy 12:3). Then in 12:4, Moses said, “You shall not act like this toward the LORD your God” (NASB95). In other words, Moses was saying ‘you are not to worship God this way.’ As the next verse says, “But you shall seek the LORD at the place which the LORD your God will choose from all your tribes, to establish His name there for His dwelling, and there you shall come” (Deuteronomy 12:5). This instruction makes the point that we are to worship God the way He tells us.

This is contrasted with Deuteronomy 12:8, “You shall not do at all what we are doing here today, every man doing whatever is right in his own eyes,” language echoed in the book of Judges (Judges 17:6; 21:25). Instead of God’s people worshipping God however they desire, Moses gives specific rules for proper sacrifices for Israel (Deuteronomy 12:13-28). Is this not how the whole Old Testament works? It gives detailed instruction for sacrifices and the worship of God. He tells us exactly how to worship Him.

The last four verses in Deuteronomy 12 (vv. 29-32) are important for the manner of worship. Moses says that when you come into Canaan, “beware that you are not ensnared to follow them [the nations], after they are destroyed before you, and that you do not inquire after their gods, saying, ‘How do these nations serve their gods, that I also may do likewise?’” (12:30). Moses said, “You shall not behave thus toward the LORD your God, for every abominable act which the LORD hates they have done for their gods; for they even burn their sons and daughters in the fire to their gods” (12:31). We may summarize this as follows—do not look to those who do not worship the Lord for instruction as to how we are to worship the Lord.

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