From The Thirsty Theologian.
Sinclair Ferguson encourages us to get serious about sin:
Paul’s exposition [Colossians 3] provides us with practical guidance for mortifying sin. . . .
1. Learn to admit sin for what it really is. Call a spade a spade—call it “fornication” (v.5), not “I’m being tempted a little”; call it “uncleanness” (v. 5), not “I’m struggling with my thought life”; call it “covetousness, which is idolatry” (v. 5), not “I think I need to order my priorities a bit better.” . . .
2. See sin for what it really is in God’s presence. “Because of these the wrath of God is coming” (3:6). . . . See the true nature of sin in light of its punishment. . . . Take a heaven’s-eye view of sin and feel the shame of that in which you once walked (3:7; cf. 6:21).
3. Recognize the inconsistency of your sin. You have put off the “old man,” and have put on the “new man” (3:9–10). . . . New people live new lives. Anything less is a contradiction of who we are “in Christ.”
4. Put sin to death (v. 5). It is a “simple” as that. You cannot “mortify” sin without the pain of the kill. There is no other way!
But notice that Paul sets this in a very important broader context. The negative task of putting sin to death will not be accomplished in isolation from the positive call of the gospel to “put on” the Lord Jesus Christ (Rom. 13:14).
Paul spells this out in Colossians 3:12–17. Sweeping the house clean simply leaves us open to further invasion of sin. But when we understand the “glorious exchange” principle of the gospel of grace, then we begin to make some real advances in holiness. Sinful desires and habits not only must be rejected but exchanged for Christ-like graces (3:12) and actions (3:13). As we are clothed in Christ’s character and His graces are held together by love (v. 14), not only in our private lives but also in the church fellowship (vv. 12–16), Christ’s name and glory will be manifested and exalted among us (3:17).
—Sinclair Ferguson, In Christ Alone: Living the Gospel Centered Life (Reformation Trust, 2007), 220–221.