God has done what the law, weakened by the flesh, could not do…For the mind that is set on the flesh is hostile to God, for it does not submit to God's law; indeed, it cannot. Those who are in the flesh cannot please God. You, however, are not in the flesh but in the Spirit, if in fact the Spirit of God dwells in you. Anyone who does not have the Spirit of Christ does not belong to him. – Romans 8:3,7-9 ESV
This passage is spoken in context of the famous memory verse of many Christians over the centuries Romans 8:1 There is therefore now no condemnation for those who are in Christ Jesus The law was given to illuminate the depravity of our sin nature and impossibility to be pleasing to God in the flesh.
Indeed it is by Grace we are saved and by Grace that we stand.
The commands of God never made anyone good, only faith in his provision has ever made anyone good and right before God.
In regards to the law and the New Testament commands, I think where our confusion lies at times is in the difference in keeping the law for salvation (Justification) or following and obeying the commands of Christ and the principles of the law out of pure love and desire to be like God (Sanctification). These are quite opposite, one is outer self-preservation motivation and one is inner spirit motivation. If you are in Christ you will strive to follow and obey, but if you are not, you will continue in sin avoiding following him. Keeping New Testament "commands" are not our means to purity, but a result of it...evidence of it. I understand people’s desire to preach holiness and greater commitment to follow Christ and his commands, because so many people who call themselves Christians do not seem to be concerned at living in sin. So audience and context is important. It may be that these people are the “goats” or the “tares” that Jesus warned us about among the “sheep” or the “wheat” (Matthew 25:31-46, Matthew 13:24-30). As well we should preach and teach and encourage fellow Christ followers to walk in the light of obedience, for Christ himself said whoever keeps my commands, he it is who loves me (John 14:21). But we must remember this is the result of the Gospel not a way to salvation. Loving God and Jesus as Lord, our master and leader is fruit of the Spirit in us, not the other way around.
For instance murder was and still is wrong. Under the Law it brings me death and condemnation because evil hateful, careless, or reckless thoughts violate its principle of loving your fellow man, so that sin of that must be dealt with. But since Christ paid the price for my crimes of those thoughts and deeds, through faith in him, I am now justified as clean and pure. But yet even under grace, God still wants me to love my fellow man and not think or do hateful things towards him, so Christ has emphasized the greater underpinning command to love neighbor as yourself. The holiness of God and his plan for us to be like him has not changed. Once justified and accepted into the family of God, (not acceptance of our sins, but our souls) we have Holy Spirit inner motivation to be more like our Holy Father God. This is what sanctification is all about, in the setting of us apart for God as a holy people. It is a process in this life. This is our new desire. Before salvation, we just “tried” to not get caught and punished. We really were in hiding from God and tried to avoid his ominous Holiness. Now in Christ we are drawn to it. So we still have rules of living and for holiness in practical life, but these are not for our justification, but for our sanctification.
John Murry said it well… “Indeed, the more sanctified the person is, the more conformed he is to the image of his Savior, the more he must recoil against every lack of conformity to the holiness of God. The deeper his apprehension of the majesty of God, the greater the intensity of his love to God, the more persistent his yearning for the attainment of the prize of the high calling of God in Christ Jesus, the more conscious will he be of the gravity of the sin that remains and the more poignant will be his detestation of it.”
The "Law" is fulfilled in Christ so its demands for making us holy are no longer needed for our purification and legal righteousness before God. As the Bible says it’s a school master to show us the need for the Savior. When we as born-again children of God fail and sin, which we all do more often than we realize, we are never condemned by God or by the law of sin and death, but are now free from that curse. Yet we as God's beloved will face difficult chastisement and correction if we don't repent from known sin that the Holy Spirit reveals to us, which many times come to us from other godly Believers in accordance with his Word.
These commands of the New Testament are unlike the Law fulfilled by Christ. These were not given by Christ for making us righteous; we have that imputed into us without anything we have done to earn it. But the commands of Christ are our "marching orders" as in military terms for war, on to how to live for Christ as we were redeemed and created to do. We are at war with the lies of Satan and his darkness. We don't preach the commands of Christ to the unsaved, but to the saved to help them follow their Master. We don’t do it in a condemning way, but soberly and with all seriousness because our God is our Father and he does demand of us to walk in his light and will bring correction to us if we do not, but never is the true Christian under condemnation (Rom 8:1) . Just like when one of my children does wrong, I am displeased, but never will I forsake them or abandon them, but I will bring correction and do what must to help draw them towards goodness in their heart. They never need worry that I will cast them out from my love or family, as neither does a child of God never need to worry about being cast out into the utter darkness from which they came. No we are forever his. After all his Spirit birthed in us new life and God will not kill that new life, any more than I will kill my baby. The thought is absurd. But I will demand that my children live upright and do everything to ensure they do.
The Gospel is about salvation and bringing one across from death and condemnation into life, the commands of Christ are unlike the Law of old, they are simply instructions on how to follow him now that we have ability with His Spirit living in us. For those who refuse to obey Christ and live in sin, after loving exhortation to turn from sin(not condemning), we are told to treat them as outsiders. But only God knows really if they are a one of his sheep or a goat. They too should know, if they really have the Spirit in them. Yet wallowing in sin will blind them to even God and their security of salvation. This is why we see so much tension in Scripture, even the New Testament warning that our God is a consuming fire. Sometimes even a wayward backslidden Christian, like I once was, needs a little fear of the Lord restored back into their heart. Truly the fear of the Lord is the beginning of Wisdom, but perfect love, that of walking in his light, casts out all fear as we cry out Abba, Daddy, Father and climb into his holy loving arms to feel the warm hugs of his love!
For years as a child of God I walked in sin, I was a prodigal, never climbing in his arms of love, feeling so distant and ashamed of my life before him, but always knowing I had to do something and repent before his strong arm of correction destroyed my life totally. God will even take the life of a wayward child if that is necessary to keep us from polluting his people, but never ever will he forsake us. Never! For he has spoken, “Never will I leave you, nor forsake you.” (Heb 13:5, Duet 31:6) And by the grace of God, I am here today restored, because he finally got through to me by reminding me that he is a consuming fire and will bring serious correction, so never again will I return to that vileness of living unrepentant in sin. He has given me a second chance at living for Jesus, and I plan on using every day to proclaim the amazing grace and love of God in Christ! Truly this is what keeps me wanting to follow every single command of God and making progress towards that.