Why do Christians continue to sin even after being saved?

After salvation, believers experience a dynamic called 'justification,' where they are declared righteous before God based on Christ’s work. However, they still inhabit a sinful body that is influenced by the old man, which is why Paul reflects on the ongoing struggle with sin in Romans 7. The presence of two natures within every believer results in a war; the new man desires to honor God and fulfill His law, while the old man seeks to indulge sinful desires. This duality explains why even the most devout Christians struggle with sin, underscoring the need for continued dependence on God's grace and the power of the Holy Spirit to persevere in righteousness.