Galatians 5v17-18: For the desires of the flesh are against the Spirit, and the Spirit against the flesh, for these are opposed to each other, to keep you from doing the things you want to do. But if you are led by the Spirit, you are not under the law.
v16: “walk by the Spirit, and you will not gratify the desires of the flesh”, v17: “the desires of the flesh are against the Spirit, and the desires of the Spirit are against the flesh”, v19: “the works of the flesh are evident” compared with v22: “the fruit of the Spirit”, v24: “those who belong to Christ Jesus have crucified the flesh” then v25: “If we live by the Spirit, let us also walk by the Spirit”. All the way through you have the Spirit vs. the flesh, but in v18 Paul says “if you are led by the Spirit, you are not under the law”.
In previous chapters Paul’s gone on and on about the law. He’s reminded the Galatians that we’re not justified by works of the law, but through faith in Christ, and he’s been pleading with them not to go back to slavery under the law. And now, as he talks about the fruit of the Spirit, and not gratifying the desires of the flesh, he’s not finished what he had to say about the law and moved onto a separate topic; this flesh problem is related to the law problem. Being reminded that you’re not under the law is somehow helpful in the battle against the desires of the flesh.
I think it will be helpful here to look at Romans 7. I was initially just going to pick out a couple of verses, but the whole chapter expands on this battle between the Spirit and the flesh, and why it helps us to be reminded that we’re not under the law. (read it)
You would think that if you were under the law – if you believed you needed to obey it in order to gain or keep favour with God – then you would be extra obedient, but that’s not what happens. The law arouses sinful passions.
The problem is not with the law itself; the problem is you’re not being led by the Spirit. “If you are led by the Spirit, you are not under the law”. You can’t be led by the Spirit and under the law at the same time. So if you are under the law, then you must not be being led by the Spirit. And if you’re not being led by the Spirit, then the flesh has control. And if the flesh has control, then the law will just arouse sinful passions. For some people, those sinful passions aroused by the law will be obviously irreligious things like sexual immorality, drunkenness or sorcery, but there are other things on the list in v19-21 that can be just as much of an issue for people within the church: envy, dissensions, divisions. The law arouses those things in us if we’re not being led by the Spirit.
Also, looking ahead to v22-23: “the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control; against such things there is no law” – no law can make you loving or joyful or peaceful or patient. The Christian life isn’t about getting better at behaving according to certain rules; it’s about having our character become more and more like Christ’s. And that doesn’t happen when someone challenges us to work hard on getting our performance up to a higher standard; it’s the fruit of the Spirit.
So if you want to grow this fruit and become like Christ, the answer is not to put yourself under the law; you need the Spirit, and as we already saw in Galatians 3, the way we receive the Spirit is by hearing with faith. Remind yourself of the gospel of God’s glorious grace given to you in Christ, and believe it. Then the Spirit will keep pointing you to Christ, and in 2 Corinthians 3:18 Paul explains that as the Spirit points to Christ, we behold his glory, and that transforms us into the same image.
But there is a battle going on. “The desires of the flesh are against the Spirit” and that “keeps you from doing the things you want to do”. Christ calls us to freedom, but the conflict between the flesh and the Spirit means we don’t experience that freedom fully in this life. But this can actually be encouraging if you’re struggling, because the only alternative to having this battle between the Spirit and the flesh is not to have the Spirit (in other words, not to belong to Christ). If you’re struggling with the battle against the flesh, it’s not because you’re a weak Christian; it’s because you are a Christian.