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The foundation of Christianity is not any set of laws; it's Jesus Christ himself. We accept that through him God accomplished what we could never accomplish, namely, our obtaining the righteousness necessary for salvation:
Now we know that whatever the law says, it says to those who are under the law, so that every mouth may be silenced and the whole world held accountable to God. Therefore no one will be declared righteous in his sight by observing the law; rather, through the law we become conscious of sin.
But now a righteousness from God, apart from law, has been made known, to which the Law and the Prophets testify. This righteousness from God comes through faith in Jesus Christ to all who believe. There is no difference, for all have sinned and fall short of the glory of God, and are justified freely by his grace through the redemption that came by Christ Jesus. God presented him as a sacrifice of atonement, through faith in his blood. He did this to demonstrate his justice, because in his forbearance he had left the sins committed beforehand unpunished - he did it to demonstrate his justice at the present time, so as to be just and the one who justifies those who have faith in Jesus. (Romans 3:19-26,NIV)
The righteousness we need for salvation is a righteousness which we cannot earn as a salary or purchase as an item. Instead, we must adopt the same attitude as the tax collector in Luke 18:9-14, who implored God to be merciful to him, a sinner. And those of us who accept what God himself has already done on our behalf through Jesus Christ's sacrifice are assured that we will receive that mercy. God, who could have simply 'written us off', chose instead to do what he deemed necessary in order to save us from the consequences of our own shortcomings and enable us to have eternal life with him.
And how do we repay God for what he's done? We don't. Instead, we permit God to subdue our original, sinful nature himself, as well as implanting within us a new nature. This new nature is necessary for us to have if we are to truly have our actions conform to what God wants of us:
So I say, live by the Spirit, and you will not gratify the desires of the sinful nature. For the sinful nature desires what is contrary to the Spirit, and the Spirit what is contrary to the sinful nature. They are in conflict with each other, so that you do not do what you want. But if you are led by the Spirit, you are not under law.
The acts of the sinful nature are obvious: sexual immorality, impurity and debauchery; idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions and envy; drunkenness, orgies, and the like. I warn you, as I did before, that those who live like this will not inherit the kingdom of God.
But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control. Against such things there is no law. Those who belong to Christ Jesus have crucified the sinful nature with its passions and desires. Since we live by the Spirit, let us keep in step with the Spirit. Let us not become conceited, provoking and envying each other. (Galatians 5:16-26,NIV)
Note how many of the acts listed as 'the acts of the sinful nature' aren't really actions in-and-of themselves. Instead, they are the motivations which culminate in the commission of sinful acts. They are also at the core of our original nature, and so are as much a part of us as our eye color. If we attempt to subdue them ourselves we find that we are using one act of the sinful nature to offset another act of the sinful nature. We need the help of God himself, just as a patient in need of a transplant needs for a skilled surgeon to perform that transplant.
Just as we can say that 'the acts of the sinful nature' are the cause of all sinful acts, we can say that 'the fruit of the Spirit' is the cause of all righteous acts. And in order for our actions to be truly righteous, the impetus for those actions must itself also be righteous. One cannot pick good fruit from a poisoned tree, and likewise one cannot have a righteous act be the result of a sinful motivation. In order for our actions to be righteous, the motivations which led to their being performed must also be righteous, and that only occurs if the motivations are those found in 'the fruit of the Spirit'. That's why the words immediately following their listing are, "Against such things there is no law."