It is both relief and heartache to know that all true believers have sin remaining in them in this life. The great apostle said, “Not that I have already obtained this or am already perfect, but I press on to make it my own, because Christ Jesus has made me his own” (Philippians 3:12). In another place he said, “I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members” (Romans 7:23). And Jesus taught us to pray daily, “Forgive us our debts” (Matthew 6:12).

“Killing sin is not optional. This is mortal combat: Sin dies or we die. We refuse to settle in with sin.”

This does not mean we should become complacent about sin. It means we must fight it daily. We are commanded to constantly kill the sin that remains in our lives: “If you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live. . . . Put to death therefore what is earthly in you” (Romans 8:13; Colossians 3:5). This is not optional. This is mortal combat: Sin dies or we die. Not that we ever become perfect in this age, but we go on killing sins as they attack us from day to day. We do not settle in with sin. We fight and we kill.

How do we kill sin? Here are thirteen tactical steps in the battle:

1. Take heart from the truth that the old sinful you is decisively already dead (Romans 6:6; Colossians 3:3; Galatians 5:24). By faith we are united to Christ so that his death was our death (Romans 6:5; 2 Corinthians 5:14). This means three things: (a) The mortal blow to our “old man” has been struck; (b) the old self will not succeed in domination now; and (c) his final obliteration is certain.

2. Consciously reckon the old man dead; that is, believe the truth of Scripture about the old man’s death in Christ and seek to live in that freedom (Romans 6:11). Living out the reality that you are is the proof that you are. One clear illustration of becoming what you are is found in 1 Corinthians 5:7: “Cleanse out the old leaven that you may be a new lump, as you really are unleavened.” It sounds strange, but salvation is a strange and wonderful thing: Clean out the old leaven of sin, because it is really already cleaned out. If you try to play logic games with this reality and say, “I don’t need to fight sin because it is already cleaned out,” you will prove only that you are not among the number who are cleansed.

3. Cultivate enmity with sin! You don’t kill friends (Romans 8:13). You kill enemies. Ponder how sin killed your best Friend (Jesus), dishonors your Father, and aims to destroy you forever. Develop more hatred for sin.

4. Rebel against sin’s coup. Refuse to be bullied by its deceits and manipulations. “Let not sin therefore reign in your mortal body, to make you obey its passions” (Romans 6:12). Temptations to sin are all half-truths and half-lies at best. Paul calls their fruit (literally) “lusts of deceit” (Ephesians 4:22).

5. Declare radical allegiance to the other side — God — and consciously put all your mind, heart, and body at his disposal for righteousness and purity. “Present yourselves to God as those who have been brought from death to life, and your members to God as instruments for righteousness” (Romans 6:13).

6. Don’t make any plans that open the door for sin’s entry. “Make no provision for the flesh, to gratify its desires” (Romans 13:14). Don’t prove your purity in a pornography shop or your commitment to simplicity at an upscale mall.

7. Know the spirit of the age and consciously resist conformity to it (Romans 12:2). As D.L. Moody said, “The ship belongs in the water of the world, but if the water gets in the ship, it sinks.”

8. Develop mental habits that continually renew the mind in God-centeredness (Romans 12:2; 2 Corinthians 4:16). Fix attention daily on “the things of the Spirit” (Romans 8:5), the “things that are above” (Colossians 3:2). Let your mind dwell on whatever is true, honorable, just, pure, lovely, gracious, excellent, and worthy of praise (Philippians 4:8).

9. Admit failure and confess all known sin every day (1 John 1:9). Ask God for forgiveness (Matthew 6:12).

10. Ask for the Spirit’s help and power in all these things. “By the Spirit . . . put to death the deeds of the body” (Romans 8:13). All that is good in us is a “fruit of the Spirit” (Galatians 5:22). He causes us to walk as we should (Ezekiel 36:27; Isaiah 26:12).

11. Be part of a larger and a smaller fellowship where you are exhorted often to beware of the deceitfulness of sin (Hebrews 3:13). Perseverance in faith is a community project. We have no warrant to think we will make it to heaven if we neglect the appointed means of mutual encouragement and warning.

12. Fight your sinful impulses with all your might as a boxer fights an opponent and as a marathon runner fights fatigue (1 Corinthians 9:27; 2 Timothy 4:7).

13. Beware of “works of the law” (Galatians 3:2, 5), but let all your warfare be the “work of faith” (2 Thessalonians 1:11). That is, let your fight against sin spring from your confidence in the superior pleasures of all God promises to be for you in Christ.