We have seen how the worthy walk pertains to church unity and maturity (4:4–16). Here, Paul turned to how the worthy walk—purity—affects personal holiness. These aren’t a handful of helpful hints you may or may not want to try if the time feels right. He is giving the Lord’s commandments for how His people must live, and “together with the Lord” points to Paul’s source of authority—the Lord Himself—to speak on such matters.
Paul painted a picture of a life before Christ to reiterate that when you become a Christian, there must be a distinct break from the past. This is not a matter of eliminating sinful behavior and replacing it with moral behavior, although that will follow. Becoming a Christian is a matter of receiving new life from God (John 3:16). A clear difference should be noticeable to those around you, prompting the question: “Wait, what happened?”
In verse 17 Paul made a general statement about how unbelievers live, “in the futility of their minds.” To live in the futility of the mind is to think and live without any regard for God, for eternity. It is to live selfishly, without regard to consequence. It is to live and leave God out. Do you live as if God exists? Do you live as if Christ died for your sins?
Now take it back a notch, and see that the reason unbelievers live in the futility of their mind is that they are darkened in their understanding and alienated from the life of God. The reason they are alienated from the life of God is that deep within, they are ignorant of God. The reason for this ignorance is that their hearts are hardened—calloused—due to sin. To become callous means to cease to feel pain; thus, spiritually, it is to “lose the capacity to feel shame or embarrassment.”