Separation (7): If unrepentant and disobedient people will not enter the kingdom of God and will instead face the wrath of the God (5:5-6), how should we relate to them? Paul draws the obvious logical conclusion: “Therefore do not become partakers with them.” This is a call to separation. We loathe the wicked deeds of disobedience. We are “saints” (5:3). A reversion to our former life of sin is unthinkable! Now, this is a separation from sin, not a separation as in disassociation. We are to engage with unbelievers. We are to speak to them the truth of Christ and help them see their lost condition in sin.
Light (8-10): We must be alert about our identity as the people of God. Using the metaphor of light and darkness, Paul reminds us just how different we are from the sinful people we were before. We were formerly characterized by sin (“darkness”) but now we are characterized by holiness (“light”). This is our new identity “in the Lord.” It is in Christ that we were chosen for holiness (1:4) and made into God’s workmanship for good works (2:10). It is because of Christ that we get to bear the fruits of goodness, righteousness and truth. And we do this with ardent love for Christ. We are ever trying to learn what pleases Him. We love Him and want nothing more than to make Him happy!
 “Do not be” is more accurately “do not become [gi-no-mai (γίνομαι)].” This is a warning against falling away.
 As the hymn goes, there is for us: “no turning back, no turning back.” Cf. Rom. 6:2; 1 John 3:9; 2 Pet. 2:21-22.
 We are not to partake of their deeds (5:11; cf. also 1 Pet. 4:3-4). Elsewhere we are explicitly told to engage with unbelievers for the sake of a gospel witness. Cf. 1 Cor. 5:9-10; 10:27; Col. 4:5-6.
 We are to even expose (as in reprove/rebuke them for) their wicked deeds (5:11). This has always been the work of those who preached the gospel (Matt. 14:3-4; Acts 17:30-31; 24:24-25).
 “Light” is a metaphor for holiness (vs. sin) and not God Himself (lowercase in ESV & NKJV). “Children of light” are those characterized by holiness, as “sons of disobedience” (5:6) are characterized by disobedience.
 These reflect the character of God after whose likeness we have been made anew (4:24). God is good (Matt. 19:17), righteous (John 17:25; Rom. 3:26) and true (John 17:3; 1 Thes. 1:9), and we bear fruit in His likeness.