“Missions is not the ultimate goal of the church.” That’s how John Piper begins his book, “Let the Nations Be Glad.” It’s a shocking statement if you’ve always thought the main thing the church does is outreach. But Dr. Piper goes on, “Missions exists because worship doesn’t. Worship is ultimate, not missions, because God is ultimate, not man. “
Worship is the church’s primary purpose because it is man’s primary purpose. God made man a spiritual, worshiping being (Genesis 1:26-28). He created the universe as a theater to display his glory and made mankind to observe that glory and magnify him for it.
When Adam sinned, he caused man to inherit a corrupt nature. All men still worship, but, by nature, we worship false gods. As John Calvin put it, the sinful human heart is an idol factory. And the idol every man loves the most is himself. Christ commanded his followers to deny themselves. When we obey this command, we are killing the primary enemy against the one true God, namely, our flesh.
When we worship Christ, it’s a powerful temptation to think that whatever pleases us must please him. If I enjoy interpretive dance, neon lights, and little Suzy’s solo, surely Jesus must. Approaching worship this way is self-centered, not Christ-centered. As God sanctifies us, he aligns our affections with his, but we are never free to depart from the clear testimony of his Word. His Word becomes our delight (Psalm 119:14).
Leviticus 10 illustrates this point. Two of Aaron’s sons, Nabab and Abihu, “offered unauthorized fire before the LORD, which he had not commanded” (Leviticus 10:1). When they did this, “fire came out from the LORD and consumed them, and they died before the LORD” (Leviticus 10:2). Because these two men sought to worship God in a way he did not command, God took their lives. Why? God explained, “Among those who are near me I will be sanctified, and before all the people I will be glorified” (Leviticus 10:3).
Someone might say, “But that’s the Old Testament!” Well, when you turn over to Hebrews 12, the writer says, “…let us offer to God acceptable worship, with reverence and awe, for our God is a consuming fire” (Hebrews 12:28-29). What consuming fire do you think he’s reflecting on, here? He isn’t referring to the believer’s internal zeal, but the consuming fire of Leviticus 10:1 that killed Nadab and Abihu.
The principle that informed the church’s worship under the Old Covenant continues to inform our worship under the New Covenant. We must approach God with reverence for his holiness, only offering in worship the things he authorizes in Scripture.
Therefore, you can tell what a church believes about Scripture’s authority by looking at its worship. Jesus condemned the Pharisees for “teaching as doctrines the commandments of men” (Matthew 15:9). This is what the church does when it incorporates unbiblical elements of worship. When worship conforms to Scripture, Christ is exalted in the church. When Christ is exalted in the church, he strengthens believers and draws men to himself.
 John Piper, Let the Nations Be Glad! The Supremacy of God in Missions (Grand Rapids, Mich: Baker Books, 1993), 11.