‘This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.’ — Galatians 5:16
The law of Moses cannot save; neither can it sanctify. Those who realise that law observance has no part in salvation need to also realise that the law has no power to help us live out our salvation.
Sometimes Christians mistakenly think that observing parts of the law of Moses (such as the ‘moral’ aspects of it) or creating another system of laws and rules will help a person live a holy life. This is not what the Bible teaches.
The law of Moses is a complete package. To put oneself under any part of it for salvation or sanctification is to be obligated to the entire law (v.3) and to misunderstand the truth (v.7) about its purpose (Gal 3:24).
The believer in Christ is not under law but under grace. God gives all believers His Holy Spirit who works within them. As they walk in the power of the Spirit, they will not fulfil the lusts of the flesh (v.16). The believer does not need the law, because he is led by the Spirit (v.18), and the Spirit will produce righteous fruit in them (v.22-23).
So, stop trying to live your Christian life by the power of law. Realise that, in Christ, your flesh with its affections and lusts was crucified with Christ, and you now have the power of God’s Spirit changing you from the inside out (v.24-25).
If we fail to live righteously as believers, the solution is not more laws/rules. Instead, we need more truth about who we are in Christ, more appropriation of those truths, and more dependence on the Spirit of God.