If the heart is as central as Scripture says it is, then a pressing question follows: how does the heart change? How can a love for sin be exchanged for a love for God? How can Christians grow in holiness, not merely in outward behaviour, but in the deep desires that drive behaviour?

From outside-in to inside-out
The Pharisees believed transformation worked from the outside in. Change behaviour, enforce conformity, and the heart would follow. Yet Scripture shows that the Spirit works in the opposite direction. He brings change from the inside out.

Romans 8 describes this transformation. Those who were once hostile to God are brought to cry, “Abba! Father!” (Romans 8:15). The Spirit does not simply restrain sin or polish conduct. He turns enemies into children, changing people by reshaping what they love and enjoy, so that obedience flows from new desire rather than external pressure.

This difference matters deeply, both for ministry and for the Christian life.

The aim of preaching
Charles Spurgeon warned preachers that they are not sent to “whiten tombs,” but to open them. Outward moral improvement can be achieved through pressure, fear, and expectation. But such change often produces hypocrisy rather than holiness, behaviour driven by self-reliance and self-righteousness.

Ministers of the new covenant, Paul says, are ministers of the Spirit (2 Corinthians 3:6). Their aim must match the Spirit’s. Spurgeon put it this way: the object of all true preaching is the heart. The goal is not merely better behaviour, but hearts that are loosened from sin and bound more firmly to Christ.

What God is like
Why must heart-change be central? Because of what God is like. Jesus answers this directly when he prays, “Father, you loved me before the foundation of the world” (John 17:24). Before creation, the Father is eternally loving, rejoicing, and satisfied in the beloved Son.

If this is who God is, then nothing will make a person more Godlike than love for Jesus Christ. Godliness is not first a matter of external correctness, but of holy affection. To grow in likeness to God is to grow in love for what he loves.

True religion and holy affections
Jonathan Edwards famously argued that “true religion, in great part, consists in holy affections.” True Christians are those whose hearts have been reshaped by the Spirit, whose desires now move toward Christ.

This is why preaching must do more than explain doctrine. Edwards insisted that God ordained preaching so that divine realities would be pressed upon the heart. Scripture is to be opened and applied in such a way that love for Christ and joy in him are awakened, not just acknowledged.

To speak of affections is not to endorse emotional manipulation. Edwards carefully distinguished between emotions and affections. Emotions are often reactive and change quickly with circumstance, fatigue, or physical condition. Affections are deeper and more constant. Over time, they shape emotions, even though they do not prevent every low or heavy day.

This distinction is pastorally important. Raised intensity or visible excitement is not the same thing as heart renewal. Preaching should be affecting, but not artificial. It must refuse shortcuts that confuse emotional reaction with spiritual transformation, while also refusing to leave people indifferent to Christ.

Gospel power for sanctification
Christians often answer quickly when asked how hearts change: through the gospel, “the power of God for salvation” (Romans 1:16). Yet Scripture makes clear that the gospel’s work does not end at conversion.

Paul writes that “the grace of God has appeared, bringing salvation… training us to renounce ungodliness and worldly passions, and to live self-controlled, upright, and godly lives” (Titus 2:11–12). Grace does not step aside once someone believes. It continues its work, shaping and reforming the heart over time.

Scripture speaks in both commands and promises, law and gospel. God’s commands show us what holiness looks like. They matter. But commands alone cannot change desire. The law can restrain behaviour and expose sin, but it cannot soften the heart. Only the gospel does that.

John 3 and the sight that changes
John 3 provides a clear picture of how the Spirit works. Nicodemus is baffled when Jesus tells him he must be born again by the Spirit. Jesus implies that this should not be new to him, pointing back to the promise of the new covenant: “I will give you a new heart… and put my Spirit within you” (Ezekiel 36:26–27).

When Nicodemus still does not understand, Jesus directs his attention to the cross: “As Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up… For God so loved the world” (John 3:14–16).

It is this sight that transforms hearts. At the cross, self-righteousness collapses as the seriousness of sin is exposed. Sin is seen for what it truly is. Yet at the same time, the cross displays an unexpected kindness in God. The God many fear as an unkind judge is shown to be gracious, generous, and self-giving. Love rises in response: “We love because he first loved us” (1 John 4:19).

As Christ’s beauty becomes vivid, sin loses its charm. What once seemed sweet begins to look empty and destructive. Demands may curb behaviour for a time, but only grace can reorder love.

The glory that wins the heart
Many imagine God’s glory as something like an inflated celebrity status, demanding applause. The cross redefines glory. Jesus says that his hour of glory is the hour of his self-giving death (John 12:23–24). This is a glory of overflowing fullness that gives life.

Luther captured the heart of the gospel with clarity: God’s love does not find people attractive and then love them. It loves, and in loving bestows good. Sinners are not loved because they make themselves attractive. They become attractive because they are loved.

The secret of godliness
Paul calls this “the mystery of godliness”: “He was manifested in the flesh… believed on in the world, taken up in glory” (1 Timothy 3:16). The secret of holiness is a person, Jesus Christ himself.

Ministry can easily turn people inward, urging them to fix themselves, even in the name of discipleship. Service for Jesus can overshadow communion with him. The remedy Scripture offers is a fresh view of Christ’s glory by faith, an abiding in him, and renewed delight in the one who is the source of life.

Hearts change as Christ is lifted up before the church. As people behold him more clearly, the Spirit draws them into deeper affection and a growing desire to belong to the one who loved them first.