Two commands are offered in this verse. First, believers are to completely avoid participating in sin. Paul’s command here implies that sin is a waste of time and associated with darkness, which is opposed to the light of those living for Christ.
The second command is a contrast to merely avoiding sin. This instruction means to unmask or point out what is sinful. This does not mean speak in graphic detail about certain sinful actions (Ephesians 5:12). However, believers must define right and wrong and encourage others (and themselves) to live according to what is right. This is a powerful counter to the frequent charge against Christians of being “judgmental.” While we must use righteous, humble judgment (John 7:24), we are actually commanded as believers to point out sin, for the benefit of others (James 5:20).
This need to expose sin requires believers to avoid particular actions, encouraging purity and unity in the body of Christ. This includes a careful personal life (Ephesians 5:15), wisdom (Ephesians 5:15), a productive use of time (Ephesians 5:16), focusing on God’s will (Ephesians 5:17), and joining together with other believers for worship (Ephesians 5:18–20).
Chapter 5 begins with an admonition to imitate Christ. In order to do so, Christians must avoid sexual immorality, vulgar language, foolishness, and other inappropriate attitudes. Paul warns that those who persist in these behaviors are not part of the kingdom of God. The passage then transitions to an explanation of mutual submission, including that between husbands and wives. Wives are to submit to their husbands, and respect them. Husbands are to love their wives in a Christ-like, sacrificial, and humble way.
Ephesians 5:1–21 continues Paul’s invaluable instructions on how Christians should live out their faith. Rather than imitating the world, or being controlled by worldly things, Christians are to be filled with the Spirit. Specific flaws such as sexual immorality, crude speech, and wasting of time are discouraged. Instead, believers ought to submit to one another out of respect for Christ, providing a powerful witness to the world.