Romans 7:24–25 (ESV) … “Wretched man that I am! Who will deliver me from this body of death? Thanks be to God through Jesus Christ our Lord! So then, I myself serve the law of God with my mind, but with my flesh I serve the law of sin.”
The believer has an old nature that wants to keep him in bondage; “I will get free from these old sins!” the Christian says to himself. “I determine here and now that I will not do this any longer.” What happens? He exerts all his willpower and energy, and for a time succeeds; but then when he least expects it, he falls again. Why? Because he tried to overcome his old nature with Law, and the Law cannot deliver us from the old nature. When you move under the Law, you are only making the old nature stronger; because “the strength of sin is the Law” (1 Cor. 15:56). Instead of being a dynamo that gives us power to overcome, the Law is a magnet that draws out of us all kinds of sin and corruption. The inward man may delight in the Law of God (Ps. 119:35), but the old nature delights in breaking the Law of God. No wonder the believer under Law becomes tired and discouraged, and eventually gives up! He is a captive, and his condition is “wretched.” (The Greek word indicates a person who is exhausted after a battle.) What could be more wretched than exerting all your energy to try to live a good life, only to discover that the best you do is still not good enough!
Is there any deliverance? Of course! “I thank God that there is Someone who shall deliver me—Jesus Christ our Lord!” Because the believer is united to Christ, he is dead to the Law and no longer under its authority. But he is alive to God and able to draw on the power of the Holy Spirit. The explanation of this victory is given in Romans 8.
The final sentence in the chapter does not teach that the believer lives a divided life: sinning with his flesh but serving God with his mind. This would mean that his body was being used in two different ways at the same time, and this is impossible. The believer realizes that there is a struggle within him between the flesh and the Spirit (Gal. 5:16–18), but he knows that one or the other must be in control.
By “the mind” Paul meant “the inward man” (Rom. 7:22) as opposed to “the flesh” (Rom. 7:18). He amplified this thought in Romans 8:5–8. The old nature cannot do anything good. Everything the Bible says about the old nature is negative: “no good thing” (Rom. 7:18); “the flesh profiteth nothing” (John 6:63); “no confidence in the flesh” (Phil. 3:3). If we depend on the energy of the flesh, we cannot serve God, please God, or do any good thing. But if we yield to the Holy Spirit, then we have the power needed to obey His will. The flesh will never serve the Law of God because the flesh is at war with God. But the Spirit can only obey the Law of God! Therefore, the secret of doing good is to yield to the Holy Spirit.
Paul hinted at this in the early verses of this chapter when he wrote, “That we should bring forth fruit unto God” (Rom. 7:4). Just as we are dead to the old nature, so we are dead to the Law. But we are united to Christ and alive in Christ, and therefore can bring forth fruit unto God. It is our union with Christ that enables us to serve God acceptably. “For it is God which worketh in you, both to will and to do of His good pleasure” (Phil. 2:13). That solved Paul’s problem in Romans 7:18: “For to will is present with me; but how to perform that which is good I find not.”
The old nature knows no law and the new nature needs no law. Legalism makes a believer wretched because it grieves the new nature and aggravates the old nature! The legalist becomes a Pharisee whose outward actions are acceptable, but whose inward attitudes are despicable. No wonder Jesus called them “whited sepulchres, which indeed appear beautiful outward, but are within full of dead men’s bones, and of all uncleanness” (Matt. 23:27). How wretched can you get!
The best is yet to come! Romans 8 explains the work of the Holy Spirit in overcoming the bad and producing the good.
 Wiersbe, W. W. (1996). The Bible exposition commentary (Vol. 1, pp. 537–538). Wheaton, IL: Victor Books.