The following is an excerpt from The MacArthur New Testament Commentary on Romans 8.

So then, brethren, we are under obligation, not to the flesh, to live according to the flesh-for if you are living according to the flesh, you must die; but if by the Spirit you are putting to death the deeds of the body, you will live. (Romans 8:12–13)

Putting to death the deeds of the body is a characteristic of God’s children. The Scottish theologian David Brown wrote, “If you don’t kill sin, sin will kill you.” Jesus said, “If your right eye makes you stumble, tear it out, and throw it from you; for it is better for you that one of the parts of your body perish, than for your whole body to be thrown into hell. And if your right hand makes you stumble, cut it off, and throw it from you; for it is better for you that one of the parts of your body perish, than for your whole body to go into hell” (Matt. 5:29–30). No action is too drastic in dealing with sin; no price is too great to pay in turning from sin to trust Jesus Christ and thereby escaping the damnation of eternal death in hell.

The pattern of a true believer’s life will show that he not only professes Christ but that he lives his life by Christ’s Spirit and is habitually putting to death the sinful and ungodly deeds of the body. Consequently, he will live, that is, possess and persevere to the fulness of eternal life given him in Christ.

When God ordered King Saul to destroy all of the Amalekites and their livestock, Saul did not completely obey, sparing king Agag and keeping the best of the animals. When the prophet Samuel confronted Saul, the king tried to defend his actions by claiming his people insisted on keeping some of the flocks and that those animals would be sacrificed to God. Samuel rebuked the king, saying, “Has the Lord as much delight in burnt offerings and sacrifices as in obeying the voice of the Lord? Behold, to obey is better than sacrifice, and to heed than the fat of rams” (1 Sam. 15:22). Despite the king’s pleas for mercy, Samuel then proclaimed, “The Lord has torn the kingdom of Israel from you today, and has given it to your neighbor [David] who is better than you” (v. 28). Saul’s failure to fully obey God cost him his throne.

God’s people invariably fall back into sin when their focus turns away from the Almighty to themselves and to the things of the world. For that reason Paul admonished the believers at Colossae, “If then you have been raised up with Christ, keep seeking the things above, where Christ is, seated at the right hand of God. Set your mind on the things above, not on the things that are on earth. For you have died and your life is hidden with Christ in God” (Col. 3:1–3). He then gave a partial but representative list of sins that Christians should kill by considering themselves dead to: “immorality, impurity, passion, evil desire, and greed, which amounts to idolatry. For it is on account of these things that the wrath of God will come, and in them you also once walked, when you were living in them. But now you also, put them all aside: anger, wrath, malice, slander, and abusive speech from your mouth. Do not lie to one another, since you laid aside the old self with its evil practices, and have put on the new self who is being renewed to a true knowledge according to the image of the One who created him” (vv. 5–10).

Scripture offers believers many helps for avoiding and killing sin in their lives. First, it is imperative to recognize the presence of sin in our flesh. We must be willing to confess honestly with Paul, “I find then the principle that evil is present in me, the one who wishes to do good” (Rom. 7:21). If we do not admit to sin, we delude ourselves and become still more susceptible to its influence. Sin can become a powerful and destructive force in a believer’s life if it is not recognized and put to death. Our remaining humanness is constantly ready to drag us back into the sinful ways of our life before Christ. Knowing that truth well, Peter admonishes, “Beloved, I urge you as aliens and strangers to abstain from fleshly lusts, which wage war against the soul” (1 Pet. 2:11). If Christians did not live in constant danger from sin, such advice would be pointless.

Because of the influence of our human weaknesses and limitations on our thinking, it is often difficult to recognize sin in our lives. It can easily become camouflaged, often under the guise of something that seems trivial or insignificant, even righteous and good. We must therefore pray with David, “Search me, O God, and know my heart; try me and know my anxious thoughts; and see if there be any hurtful way in me, and lead me in the everlasting way” (Ps. 139:23–24). Haggai’s counsel to ancient Israel is helpful for believers in any age: “Consider your ways!” (Hag. 1:5, 7).

A second way for believers to kill sin in their lives is to have a heart fixed on God. David said to the Lord, “My heart is steadfast, O God, my heart is steadfast; I will sing, yes, I will sing praises!” (Ps. 57:7). Another psalmist testified, “O that my ways may be established to keep Thy statutes! Then I shall not be ashamed when I look upon all Thy commandments” (Ps. 119:5–6). In other words, when we know and obey God’s Word, we are building up both our defenses and offenses against sin.

A third way for believers to kill sin in their lives is to meditate on God’s Word. Many of the Lord’s truths become clear only when we patiently immerse ourselves in a passage of Scripture and give the Lord opportunity to give us deeper understanding. David gives us the example with these words: “Thy word I have treasured in my heart, that I may not sin against Thee” (Ps. 119:11).

A fourth way to destroy sin in our lives is to commune regularly with God in prayer. Peter calls us to “be of sound judgment and sober spirit for the purpose of prayer” (1 Pet. 4:7). When we are faithful in these disciplines we discover how interrelated they are. It is often difficult to tell where study of God’s word ends and meditation on it begins, and where meditation ends and prayer begins.