Ephesians 5:17 - Ellicott's Commentary On The Whole Bible

Be ye not unwise. — The word here is stronger than in Ephesians 5:15; it is properly senseless, used of “the fool” (in Luke 11:40; Luke 12:20; 1 Corinthians 15:36; 2 Corinthians 11:16; 2 Corinthians 11:19; 2 Corinthians 12:6; 2 Corinthians 12:11). By it St. Paul emphasises his previous warning; then he adds the explanation that to be “wise” is to “understand what the will of the Lord is” — to know His purpose towards us and towards the world, and so to know the true purpose of our life. Hence we are told in Job 28:28, that “the fear of the Lord is wisdom,” or, more precisely, in Proverbs 9:10, that it is “the beginning of wisdom.”