Proverbs 20:9 asks the question "Who can say, 'I have cleansed my heart; I am pure and free from sin'?" (NLT). We can all identify with that. If we are honest with ourselves, we know we still sin. So why does Romans 6:18 say, "You have been set free from sin and have become slaves to righteousness"? Is this a contradiction?
Sin can be defined as "any thought, action, or attitude that falls short of God’s holiness" (Romans 3:23). Sin has many layers. There are specific actions or thoughts which are sinful. Murder, adultery, and theft are sins (Exodus 20:1–17). Even the desire to commit murder, adultery, and theft are sins (Matthew 5:21, 28). But sin goes deeper than that. We commit sins because we are sinners. Since Adam first sinned in the Garden of Eden (Genesis 2:17; 3:17–19), every person born has inherited a sin nature from him (Psalm 51:5; Romans 3:23; 5:12). We cannot help but sin because it is our nature to do so. A bird does not have to be taught how to build a nest and keep her eggs warm. It is her nature to do so. A child does not have to be taught to be selfish and demanding. That comes naturally.
However, we were not created to be sinful. We were designed by God in His own image (Genesis 1:27). Humanity is His masterpiece (Ephesians 2:10; Psalm 8:4–6). We were designed to live in fellowship with our Creator. But because of sin, we cannot enter His presence (Habakkuk 1:13). When Jesus died on the cross, He took upon Himself all the sin of the world (2 Corinthians 5:21; 1 John 2:2). By taking the punishment for our sin, He cancelled the debt that each of us owes God (Colossians 2:14). He also reversed the curse of our old natures, which keeps us enslaved to sinful passions and desires (Galatians 3:10, 13). Before a person meets Christ, he or she is enslaved by that sin nature (Romans 7:25; 2 Peter 2:19). At the moment of conversion, we are given a new nature that has been freed from sin (Romans 6:18; 8:2). The entire chapter of Romans 6 explains this in detail. Verse 14 says, "For sin shall no longer be your master, because you are not under the law, but under grace."
To be free from sin means that those who have made Jesus the Lord of their lives are no longer enslaved by sin. We have the power, through the Holy Spirit, to live victoriously over sin (1 Corinthians 15:56–67; Romans 8:37). Just like we once followed fleshly desires, those who are "in Christ Jesus" now follow the Holy Spirit (Romans 8:14; Galatians 5:24). Because we live in a fallen world and are still fleshly creatures, we will still sin (1 John 1:9; 2:1; Romans 7:21–22). But those who follow Christ do not make sin a lifestyle choice (1 John 2:1–6; 3:6–10; Romans 6:2).
Those who have been born again (John 3:3) have received a new nature. Whereas the old nature drew us toward self-pleasure, the new nature tugs us toward holiness (2 Corinthians 5:17). To be free from sin means it no longer wields the power it once did. The stranglehold of selfishness, greed, and lust has been broken. Freedom from sin allows us to offer ourselves as willing slaves of the Lord Jesus Christ, who continues to work in us to make us more like Him (Romans 6:18; 8:29; Philippians 2:13).