Why - and how - is love the fulfilling of the Law? Some have tried to live as though the Law fulfills love, which will utterly fail to fulfill the genuine love of God (Romans 13:8-10).
The answer lies in what love really is (to be a little redundant), and what the love of God does. If we possess the love of God, we do not have to struggle to perform works of the Law. Obeying God's laws will become automatic - because that is what Love does. If we attempt to fulfill love by focusing only on the Law, we will miss love. This becomes, in the final result, legalism. However, we cannot fill ourselves with the love of God (another form of legalism). Being filled with the love of God is a result of being filled with the Holy Spirit, which is a gift from God.
We sometimes hear someone explain why they do what they do by the simple statement "because that is what I do". Likewise, that is what God does, and therefore that is what love does - it fulfills the Law. This is what James is explaining when he says that his works would show that he had faith (James 2:18). Likewise, our obedience to God's law shows that we have the love of God dwelling in our hearts. If we are disobedient in some way, there is a deficiency of love in us, or a lack of yielding to Love. Living a life of love-action proves our possession of the love of God. To coin a phrase the two go together like a horse and carriage, as love and marriage should also.
Pure love is incapable of injuring at any time, under any circumstance, with everyone under all conditions. Is it any wonder that God IS love. Even when God must use "tough love", it is never injurious because all acts and attitudes of love are remedial - all is for good. All is for love. When love reigns supreme, all is love. Our sublime and true destiny is to become love personified. To be the love of God, love must take on motion, action, and volition. Words, melodies, emotional feelings in our world are used to represent love. However, the ideal of love that is presented and promoted in support of "love" are seldom realized in reality, or proven in deeds and actions. It would be wonderful if the reality was lived out according to the emotion expressed. In romance, in marriage - and in religion - the reality is sadly lacking today. Oh, there is an abundance of lust, deceit, and manipulation, and self gratification masquerading as love. Pure serving of the self. And many times at someone else's expense. Love - if love fulfills the Law - must be moving, in action. But where is this real love in action?
There is little love in action because there is little of God, Who is love. The problem of Law without love is that one can become a well-ordered shell. The best definition of a well-ordered shell is a robot. A robot is very efficient (at least the good ones are...), very exacting, and very programmed, perfect in obedience. This would also adequately describe a human living perfectly under the Law, if it were possible to do so, which it is not. Under the Law without love is programmed obedience, and for humans this causes tension, stress, and striving due to the impossibility of reaching perfection.
The Law, and law per se, is useful. It is useful in defining failure, or measuring success. It is useful in defining direction (1 Timothy 1:9). It cannot prevent failure, but it gives us direction. Otherwise there would be no order, system, concerted accomplishment, or lead us toward the destination of Love, and tell us what the fruit of Love will look like. It is useful also as a restraint, to keep a lid on the fallen nature long enough until a permanent reprogramming of our nature is accomplished. There must law in human societies, as long as there is the fallen (human) nature. Human nature without respect and submission to law is anarchy, in which any society will eventually self destruct. There is one coming in the future whom the Bible calls the "man of lawlessness" who will not be governed by anything but Satan - and Satan was and is utterly lawless. He is completely loveless.
In many ways, the more we strive to please God and show that we love Him thereby, the more we show we do not. Hence the futility of striving to fulfill love with the Law. God’s Law is perfect, but we are not. Jesus came to do for mankind what the Law is powerless to do: to change the nature of man. Law can affect a habit of lawfulness, but the inner man it will not change permanently. It cannot give us a new nature. The imperfect is incapable of being perfect lawfully. It is a contradiction. It converts (turns - RV) the soul, and gives wise direction toward salvation (Psalm 19:7) - IF...if it is administered by God through the Holy Spirit. It is a matter of direction. Love - the love of God in Christ - overlays the Law, and because the "law is spiritual", without the Spirit of love it too will fail to affect a permanent change in our natures. This is abundantly pictured in the Biblical history of Israel.
Those who truly keep God’s Law by Love do not even know they are keeping it, because it is coming down from God, and goes back to Him. It is then automatic - Love becomes the Law. The Law becomes Love. The two are united in One. Obedience becomes the "Natural" response, conduct, thought and motive. Therefore, love is law-keeping. Love is character. Love is how we know right character. There is bad character, which is lawless character, because, it is law-less. God's Law, unless fulfilled, leads us to be condemned because human nature cannot apprehend His Law without breaking it. This is sin. And the penalty of sin is death. Therefore, someone or something must intervene, or we are all condemned (Romans 6:21-23).
There is a long held misunderstanding concerning character. Character (good character), has been referred to as forcing yourself to do right no matter what the circumstance. This is incorrect. Forcing ourselves to do something is not necessarily character. It is will-power. This is the classic misconception of the legalistic mindset. Good character is doing automatically what is right without force of volition. It is an automatic response. Love results in movement within the bounds of Law. Movement implies law - breaking it or keeping it. But God is Love. Therefore, God and love are lawful (1 Corinthians 13).
The Law of God can guide us, inform us, and even restrain us - but it was never intended to, cannot, and will not change us permanently - unless God (Who IS Love) is fulfilling it (the Law) in us (Colossians 1:27). We will be living out God’s standards, basically defined by the Law, without even realizing that we are doing so. Our thoughts, actions, and responses to any and all things in life will more and more be fulfilling God’s Laws, because Christ’s Love is more and more filling us.
Use God’s Law to educate your conscience, give you a spiritual checkup, and to prod you toward repentance (Romans 7:7). But if you focus only on the Law as an end in itself, you will miss the Law - and Love. Our only hope and focus must be on Christ - on the "law of Christ" in us, our only hope of glory and eternal life (Galatians 3:17; 5:4).
The purpose of the Law is Knowledge - not of the Law itself, but of sin, so that there may be a basis for repentance, of a spiritual reality that cannot be seen (Romans 7:7-12).
This is God’s purpose. This is His will for us, and His will in us (Galatians 5:22-23; 6:2). It is our destiny to become love, as God is love. His Law can be fulfilled in no other way.
"For I endorse and delight in the Law of God in my inmost self [with my new nature]. But I discern in my bodily members [[d]in the sensitive appetites and wills of the flesh] a different law (rule of action) at war against the law of my mind (my reason) and making me a prisoner to the law of sin that dwells in my bodily organs [in the sensitive appetites and wills of the flesh]. O unhappy and pitiable and wretched man that I am! Who will release and deliver me from [the shackles of] this body of death? O thank God! [He will!] through Jesus Christ (the Anointed One) our Lord! So then indeed I, of myself with the mind and heart, serve the Law of God, but with the flesh the law of sin."- Romans 7:22-25