“For you were once darkness, but now you are light in the Lord. Live as children of light” (Ephesians 5:8)
There are a number of beautiful metaphors used in the Bible describing those who have become true “children of God” (1 John 3:10) by the new birth. As children tend to take on the characteristics of their parents as they grow, so God’s spiritual children should be growing in the grace of God and the knowledge of God (2 Peter 3:18).
Similarly, Christians are called “children of light, and the children of the day” (1 Thessalonians 5:5). Therefore, as in this text in Ephesians, we should “live as children of light.”
The Lord Jesus spoke of us as “children of the kingdom” in Matthew 13:38. We should, therefore, live and speak as those born into the kingdom of God, and as faithful subjects of the King of kings.
Christ also called us “children of wisdom” (Matthew 11:19), and this surely implies that we should, in our understanding and in our decisions, have “the mind of Christ” who “is made unto us wisdom” (1 Corinthians 2:16; 1:30).
In contrast, note the metaphors applied in the Bible to those who have not (at least not yet) become children of God by being “born again” through faith in the triune God. We ourselves once were “like the rest, we were by nature deserving of wrath” (Ephesians 2:3). We–and they–were also called “those who are disobedient” (Ephesians 2:2; also in Ephesians 5:6 and Colossians 3:6).
Unbelievers are also called “people of this world” (Luke 16:8), and even “people of the evil one” (Matthew 13:38) and “children of the devil” (1 John 3:10).
Returning to the metaphor of our text, “if we walk in the light, as he is in the light” (1 John 1:7), then we can no longer “walk in darkness,” for we have “the light of life” (John 8:12).