In this video, Dr. Michael Reeves discusses distinctions between a passion for personal holiness and legalism.
Christians need to know that the desire to grow in holiness, a passion for personal holiness, need not be at all the same thing as legalism. Legalism is the idea that God's love can be earned, that salvation can be bought. It is the idea that salvation is the consequence of holiness, that holiness, our personal holiness of life, can bring about salvation. And so, legalism is always an unloving mindset. Legalism does not love God. It uses God to buy salvation with the price of holiness.
The gospel, on the other hand, teaches us that holiness is never a cause of salvation. Holiness is the consequence of being given new life in Christ. So in Romans 6, Paul says that believers have been buried with Christ and raised to a new life. And that new life, buried with Christ and raised with Him in His resurrection, is the only place where true holiness can grow. It is a holiness that is the consequence of being made alive in Christ, not the cause of our salvation.
Paul talks in Romans 5 about how God has poured His love into our hearts by the Holy Spirit that He's given us, so that in Romans 8, believers who are led by the Spirit cry out, “Abba! Father!” (Rom. 8:15). So, the Spirit is the one who changes our hearts so that we love God, adore Him, and therefore want to walk in His ways, want to please Him, want to walk closely with Him.
We start finding holiness beautiful. Sinfulness is repellent and ugly and becomes odious to us. The Spirit changes our very desires, so that where once we found sin entrancing, beautiful, and desirable, the Spirit turns us to see. Holiness is beautiful and sin is monstrous to us. But that change of heart is a fruit of the Spirit. And true holiness is always the consequence of the Spirit working by applying the gospel to us.
So if you want to grow in holiness and avoid legalism, fix your eyes on the gospel and the grace of God shown us in the gospel. In Titus 2:11, Paul writes, “For the grace of God has been seen bringing salvation to all, teaching us to renounce ungodliness.” And so Paul shows that it is actually the sight of the grace of God that makes us want to abandon sin and chase holiness, abandon ungodliness and chase godliness, because God seems more desirable to us. That is true holiness—not trying to buy God off, but won by His grace to want Him and His ways more.