Ephesians 5:11

11.And have no fellowship. As “the children of light” dwell amidst the darkness, or, in other words, in the midst of “a perverse and crooked generation,” (Deuteronomy 32:5,) — there is good reason for warning them to keep themselves apart from wicked actions. It is not enough that we do not, of our own accord, undertake anything wicked. We must beware of joining or assisting those who do wrong. In short, we must abstain from giving any consent, or advice, or approbation, or assistance; for in all these ways we have fellowship. And lest any one should imagine that he has done his duty, merely by not conniving, he adds, but rather reprove them. (158) Such a course is opposed to all dissimulation. Where a manifest offense is committed against God, every man will be eager to vindicate himself from any share in the guilt, but very few will guard against connivance; nearly all will practice some kind of dissimulation. But rather than the truth of God shall not remain unshaken, let a hundred worlds perish.

The word ἐλέγχειν, which is translated reprove, answers to the metaphor of darkness; for it literally signifies to drag forth to the light what was formerly unknown. As ungodly men flatter themselves in their vices, (Psalms 36:2,) and wish their crimes to be concealed, or to be reckoned virtues, Paul enjoins that they shall be reproved. He calls them unfruitful; because they not only do no good, but are absolutely hurtful.