What does Ephesians 4:23 mean?

In this verse, Paul identifies the way a Christian can separate themselves from the sin and deception of their former life, also called the "old self" (Ephesians 4:22). This transformation is only possible through Christ (Ephesians 2:8–9), for those who have come to know Him as Savior (Ephesians 4:21), and when a person commits their mind and heart to it. Paul often speaks of the importance of being "renewed," particularly in one's thinking (Romans 12:2, Colossians 3:10). This is a powerful and ongoing aspect of our relationship with Christ (2 Corinthians 4:16; Titus 3:5).

Paul's closest parallel to this concept is found in Romans 8:5: "For those who live according to the flesh set their minds on the things of the flesh, but those who live according to the Spirit set their minds on the things of the Spirit." The believer is called to live by the Spirit by focusing his or her mind on what is godly. This includes the believer's thoughts and actions. Those who do are "created after the likeness of God" (Ephesians 4:24).