Albert Barnes on Ephesians 5:13

But all things that are reproved. Marg., discovered. The word here used properly means proved, demonstrated, reproved, or convicted, Jn 16:8; but it seems here to be used in the sense of disclosed, or discovered. The sense is, that its true nature is demonstrated; that is, it is made known.

Are made manifest by the light. The sense is, "Light is the means of seeing what things are. We discern their form, nature, appearance by it. So it is with the gospel---the light of the world. It enables us to see the true nature of actions. They are done in darkness, and are like objects in the dark. Their form and nature cannot then be known; but, when the light shines, we see what they are." Comp. Jn 3:20, Jn 3:21.

For whatsoever doth make manifest is light. "Anything which will show the real form and nature of an object deserves to be called light." Of the truth of this no one can doubt. The meaning in this connexion is, that that system which discloses the true nature of what is done by the heathen deserves to be considered as light; and that the gospel, which does this, should be regarded as a system of light and truth. It discloses the odiousness and vileness, and it stands thus in strong contrast with all the false and abominable systems which have upheld or produced those vices.

(1) "reproved" "discovered" (c) "by the light" Jn 3:20,21