Charles Hodge on Ephesians 5:17

V. 17. Therefore, i. e. either because the days are evil; or, because ye are bound to walk as wise men. The latter mode of connection is to be preferred, because the reference is to the main idea of the preceding verses 15 and 16, and not to a subordinate clause. Be ye not, ἄφρονες, senseless, unthinking, trifling. Comp. Luke 11, 40, "Ye fools (ye unthinking ones), did not he that made that which is without, make that which is within also;" also Luke 12, 20; 1 Cor. 15, 36; 2 Cor. 11, 16, &c. In all these cases ἄφρων means one who does not make a right use of his understanding; who does not see things in their true light, or estimate them according to their relative importance. It is here opposed to συνιέντες. ‘Be ye not senseless, undiscriminating between what is true and false, right and wrong, important and unimportant, but understanding, i. e. discerning what the will of the Lord is.’ That is, seeing things as he sees them, and making his will or judgment the standard of yours, and the rule of your conduct. The will of the Lord is the will of Christ. That Lord here means Christ, is plain not only from the general usage of the New Testament, so often referred to, but also from the constant use of the word in this chapter as a designation of the Redeemer. Here again, therefore, the divinity of Christ is seen to be a practical doctrine entering into the daily religious life of the believer. His will is the rule of truth and duty.