Ephesians 5:8

(8) Ye were sometimes darkness, but now are ye light in the Lord.—This expression is unique, and far more emphatic than the more common phrases of “being,” or “walking,” “in darkness” and “in light.” (See Romans 2:9; Colossians 1:2; 1 Thessalonians 5:4; 1 John 1:6-7; 1 John 2:9-10.) For here the outward element of light or darkness is said to pervade the inner nature of the soul. (1) Christ is the “true Light,” the “Sun of Righteousness” (John 1:4-9; John 3:19; John 8:12; John 9:5; John 12:46). His servants are sometimes mere secondary lights (or “candles”) (Luke 11:33-34; Luke 11:36; John 5:35; 2 Peter 1:19), kindled from His rays; sometimes, like the moon or planets, they are said, as reflecting His light, or as having His light in them (John 12:35), to be actually “the light of the world” (Matthew 5:14), which, however, shines as a mere reflected light, so that “men glorify” not it, but “the Father which is in heaven” (Matthew 5:16). They thus become light, but only “in the Lord:” that is, as being made one with Him. (2) So, on the other hand, they who walk in darkness are said to be themselves darkness—new sources, so to speak, of the darkness which hates and quenches light, both to themselves and to others. “The light” which is in them “becomes darkness;” “and how great is that darkness!” (Matthew 6:23.) As there is a natural delight in giving light, so the reprobate state is distinguished by a horrible pleasure in spreading the cloud of delusion, sin, or unbelief, by which to hide God from man.

Walk as children of light.—So our Lord teaches, “While ye have the light, believe in the light, that ye may become children of light” (John 12:36; comp. 1 Thessalonians 5:5). “Children of light” are they who not only love the light, but also manifest the likeness of the one true Light, “the Father of Lights” (James 1:17), being His children in Jesus Christ.