God’s sovereign grace is prominent in Ephesians. Apart from Jesus, we are dead in sin, unable to save ourselves. Therefore, our Creator must resurrect our souls if we by faith are to lay hold of the righteousness of Christ, which alone gives us a right standing before God (Eph. 1:11–12; 2:1–9). While our deeds are never good enough to merit eternal life, the triune God bestows His effectual grace upon His elect so that we work for His glory. Rescued from the wrath we deserve, we are to be holy, prize truth, and love others (1:3–10; 2:10; 3:14–21; 4:1–3).
Today’s passage broadly defines life lived for God’s glory as life out of step with those who love the world. Most of those in Paul’s original audience were Gentile believers, so he does not use the term Gentiles in Ephesians 4:17 as an ethnic designation. Instead, it is shorthand for people who hate God’s law. Scripture does employ the words Gentiles and Israel to specify ethnicity; however, its use of these words to distinguish those set against the Lord from those who love Him is more fundamental. Ultimately, our ethnic heritage matters nothing before God — what counts is a new creation (Gal. 3:28; 6:15). Spiritually speaking, a Gentile who loves Christ is an Israelite, a true member of God’s people, and an Israelite who rejects Christ is a Gentile, an enemy of the one true Lord of all (Rom. 9:6–8; chap. 11).
Paul’s call not to “walk as the Gentiles do” is not a mandate to avoid non-Christians or to reject everything unbelievers enjoy (Eph. 4:17); rather, it is an exhortation to fulfill Israel’s original vocation to avoid the sins of unbelieving nations (Lev. 18). We may never violate God’s moral law, for doing so indicates ignorance of the Lord’s standards and a hardness in heart (Eph. 4:18–19). Ignorance never excuses sin, because even the worst sinner has basic knowledge of the Creator and His law (Rom. 1:18–3:20). Yet unbelievers lack the fuller understanding of God’s standards that Christians enjoy, so we rightly see non-Christians as morally ignorant, at least in a sense. Such ignorance is willful, a decision made in Adam not to know the Almighty (5:12–21), and we were once blind as well. When we live like unbelievers do, we deny the law God writes on our hearts and foolishly choose the darkness of moral ignorance over the light of His loving and holy law.
Sin affects our entire being, including our ability to love, our capacity to reason, and our physical bodies. The longer we persist in sin, the harder it is to see and do the will of God, so we must endeavor never to give in to temptation. Growth in the grace of Christ makes us increasingly willing to stand firm against ungodliness, but we make ourselves more susceptible to the influence of sin the longer we indulge it.