How do we know that our old nature must change?

In Ephesians 4, the Apostle Paul contrasts the old man, or sinful nature, with the new man, which believers are to embody after being born again. In verse 22, Paul instructs Christians to put off the old self, which is corrupted by deceitful desires. This change is fundamental because acceptance of Christ entails a transformative process where the believer's life is progressively aligned with God's will. The imperatives to abandon bitterness, anger, and malicious behavior are not mere suggestions but divine commands for all who have heard and been taught in Christ. The expectation is that through the Holy Spirit's power, believers will embrace their new identity and live out the righteousness that God requires.