Romans 8:7-8

The sinful mind [or the mind set on the flesh] is hostile to God. It does not submit to God's law, nor can it do so. Those controlled by the sinful nature cannot please God.

The reason the mind set on the flesh is death is because it is hostile to God, against God. Unbelievers reject His rule by doing what they want to do rather than what the Lord commands. The mind set on the flesh is hostile toward God; for it neither does nor can subject itself to the law of God. In other words, a concrete manifestation of this hostility to God is that the person refuses to submit to God’s word. God’s word says, “Do such and such.” And the hostile mind says, “Well, I don’t want to, so I won’t.” God’s word says, “Don’t do such and such,” and the hostile heart says, “Well, I want to and I will.” The concrete manifestation of hostility to God is a resistance of His Word, a resistance of His rule.

Paul says that the pagan mind is not even able to subject itself to the law of God. It is morally impossible for the unbeliever to subject himself to the law of God. Now you might be thinking, “Well, that doesn’t seem fair. God holds him responsible for it. Why would He do that if it’s morally impossible for him to do?” Paul is not saying, “Well, somehow there’s this grand scheme whereby God forbids people from doing what they want to do.” He’s pointing to the heart again, and he’s saying, “Look, if your heart is set on the things of the flesh, it is impossible for your heart to at the same time be set on the things of God, the things of the Spirit.” Jesus said, “You cannot serve both God and mammon.” It’s impossible. It’s a moral impossibility to seek after the things of God while you are wholeheartedly seeking after the things of the flesh.

Paul says in v8 that it is absolutely impossible to please God and love the flesh and love mammon at the same time. The believer, in contrast to the unbeliever, does subject his mind to the law of God. The mind of the believer is subject to the law of God. He has a reverence, a love for, a subjection to the law of the Lord. It’s the mark of the Spirit. He wants to be a Bible Christian. He wants to obey what God commands in His Word. Whereas the unbeliever is not even capable of subjecting himself to the law of God, the believer is able. Because of the Spirit’s change of our hearts, we love the law. And notice the believer in v8 is able to please God in contrast to the believer, and he does. The Christian loves to fulfill the law, the Christian loves to fulfill his chief purpose in life, his chief end in life, to glorify God and enjoy Him forever. It’s something that he delights in. God’s work of saving grace always produces a heart change in believers that manifests itself in their lives so that their attitudes, their goals, their purposes are different from those who are unbelievers. Working backwards from v8-4, we see the 5 step process: hostility, life, a spiritual mindset, a new walk in the Spirit, fulfilling the law in love. Fulfilling the law is evidence of grace.