Charles Hodge on Ephesians 5:11

V. 11. The apostle having in the previous verse insisted on the duty of Christians of so walking as to show by their works that they were the subjects of divine illumination, adds here a statement of their duty in reference to the sins of those still in darkness. Those sins he calls "the unfruitful works of darkness." By unfruitful is meant not merely barren or worthless, but positively evil. For in a moral subject the negation of good is evil. Works of darkness are those works which spring from darkness, i. e. from ignorance of God; as "works of light" are those works which light or divine knowledge produces.

The duty of Christians in reference to the works of darkness is twofold; first, to have no communion with them; and secondly, to reprove them. The former is expressed by the words μὴ συγκοινωνεῖτε, have not fellowship with them. Those who have things in common; who are congenial; who have the same views, feelings, and interests; and who therefore delight in each other’s society, are said to be in fellowship. In this sense believers have fellowship with God and with each other. So we are said to have fellowship in any thing which we delight in and partake of. To have fellowship with the works of darkness, therefore, is to delight in them and to participate in them. All such association is forbidden as inconsistent with the character of the children of light. Our second duty is to reprove them. Ἐλέγχεινis not simply to reprove in the sense of admonishing or rebuking. It means to convince by evidence. It expresses the effect of illumination by which the true nature of any thing is revealed. When the Spirit is said to reprove men of sin, it means that he sheds such light upon their sins as to reveal their true character, and to produce the consequent consciousness of guilt and pollution. In Paul says the effect of intelligible preaching of the Gospel is conviction—which is explained by saying "the secrets of the heart are revealed." The duty, therefore, here enjoined is to shed light on these works of darkness; to exhibit them in their true nature as vile and destructive. By this method they are corrected; as is more fully taught in the following verses. The ethics as well as the theology of the Bible are founded on the principle, that knowledge and holiness, ignorance and sin, are inseparable. If you impart knowledge you secure holiness; and if you render ignorant you deprave. This of course is not true of secular knowledge—i. e. of the knowledge of other than religious subjects; nor is it true of mere speculative knowledge of religious truth. It is true only of that knowledge which the Scriptures call spiritual discernment. Of that knowledge, however, intellectual cognition is an essential element. And so far as human agency in the production of the conviction of sin is concerned, it is limited to holding forth the word of life; or letting the light of divine truth shine into the darkened minds of men, and upon their evil deeds.