Day 4: Doctrine Sanctifies

Scripture Reading:

“Sanctify them in the truth; Your word is truth.” – John 17:17, LSB

When Jesus prayed for His disciples on the night before His death, He asked His Father to sanctify them. Sanctification means being set apart for God’s purposes and growing in holiness. Notice how Jesus says this will happen: through the truth of God’s Word. Holiness is impossible apart from doctrine, because doctrine is simply God’s truth taught and applied.

Many think of doctrine as cold or lifeless, but here Christ shows us its vital role: doctrine sanctifies. Without sound doctrine, believers may try to grow by feelings, traditions, or cultural habits, but these cannot produce holiness. Only God’s Word, rightly taught and believed, has the power to transform the heart.

Louis Berkhof observed, “Doctrine and life are inseparably connected. A sound faith is the only safeguard for a sound morality” (Systematic Theology, p. 25). If we lose truth, we will lose holiness. History bears this out. When the church neglected doctrine in the Middle Ages, superstition and immorality spread. But when the Reformers restored sound teaching—Scripture alone, grace alone, faith alone—the church was renewed in holiness and mission.

John Calvin wrote that Scripture is “the school of the Holy Spirit” (Institutes, 1.6.3). In that school, the Spirit not only teaches us what is true, but shapes our hearts to live by it. That is sanctification: truth applied to life. It is not enough to admire doctrine at a distance; we must receive it, believe it, and obey it.

R.C. Sproul put it simply: “The purpose of theology is doxology. We study the truth of God in order to worship God more deeply” (Everyone’s a Theologian, p. 2). True holiness is not joyless moralism, but worship flowing from hearts conformed to truth. Doctrine leads us to know Christ more, and knowing Him changes us.

This is why Paul urged the Colossians, “Let the word of Christ dwell in you richly” (Col. 3:16). The more God’s Word fills us, the more we are sanctified. To neglect doctrine is to stunt our spiritual growth. But to love doctrine is to open ourselves to God’s transforming power.

Beloved, the church does not need less doctrine to be holy; she needs more. Not human rules or empty traditions, but God’s truth faithfully proclaimed and believed. Every sermon, every Bible study, every catechism lesson is God’s means of sanctifying His people. If we long for holiness, we must long for doctrine.

Personal Reflection

1. How does John 17:17 show the connection between truth and holiness?

2. Why is it impossible to grow in holiness apart from sound doctrine?

3. Can you think of times in church history when holiness declined because truth was neglected?

4. How can you let the Word of Christ dwell in you richly this week?