Charles Hodge on Ephesians 5:12

V. 12. These works of darkness should be thus reproved, "for it is a shame even to speak of those things which are done of them in secret." There are two reasons why sins are called works of darkness. The first and principal one is, as before remarked, because they spring from darkness or ignorance of God; and the second is, because they are committed in darkness. They shun the light. The exceeding turpitude of these sins the apostle gives as the reason why they should be reproved.