Why is this the Greatest Commandment?

Matt 22:36-38 "Teacher, which is the greatest commandment in the Law?" Jesus replied: “‘Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment." (NIV)

Why is this commandment the greatest? What sets it before and above all others?

The fact that God has a “greatest” commandment tells us God has a hierarchy of commandments and a hierarchy of purpose. A God who is omniscient and omnipotent must also be omni-purposeful -- meaning he has a purpose for everything that exists (yes, even evil). What then is God’s ultimate purpose? What motivates his actions? What is he most passionate about? Others have scaled the heights of this question (Jonathan Edwards, John Owen to name two) so what I say will only be a faint echo of their words, and I hope an echo of scripture.

For my part, I would start with Christ. Certainly the greatest purpose of God must be found in his greatest works. And the greatest works of God are in revealed in Christ. The incarnation of God is  surely greater even than the creation of the universe. The incarnation is the creator stepping into his creation to reveal himself.   Jesus said, “Anyone who has seen me, has seen the Father,” (Jn 14:9). Paul wrote, “He is the image of the invisible God… For in Christ all the fullness of the Deity lives in bodily form” (Col 1:15, 2:9). Even more incredible, the incarnation is the creator taking the nature of a created being - man.  J.I. Packer summarized it this way:

The really staggering Christian claim is that Jesus of Nazareth, was God made man — that the second person of the Godhead became “the second man” (1 Cor 15:47), determining human destiny, the second representative head of the race, and that he took humanity without loss of deity, so that Jesus of Nazareth was as truly and fully divine as he was human.” (J.I, Packer, “Knowing God” pp.53)

So Christ, fully divine and, in union with the Father and the Holy Spirit, the only divine being, complete in all his perfections, condesends to become human.  Not just for a day, or until death.  Jesus Christ was and is both God and a human being.  This was true in the manger, on the cross, and it is true today as he sits on his heavenly throne and it will be true forever. 

Packer goes on to explain the meaning God’s  incarnation:

The key text in the New Testament for interpreting the Incarnation is not, therefore, the bare statement in John 1:14. ‘The Word became flesh and made his dwelling among us,’ but rather the more comprehensive statement of 2 Corinthians 8:9, ‘You know the grace of our Lord Jesus Christ, that though he was rich, yet for your sakes he became poor, so that you through his poverty might become rich.’ Here is stated not the fact of the Incarnation only, but also its meaning; the taking of manhood by the Son is set before us in a way which shows how we should ever view it — not simply as a marvel of nature, but as a wonder of grace… It meant love to the uttermost for unlovely human beings, that they through his poverty might become rich.” (J.I, Packer, “Knowing God” pp.58-59)

Love expressed through grace is a wonderous thing.  It brings joy to those who are loved, but is that the ultimate purpose?  When Jesus entered Jerusalem for the last time, knowing his death was imminent, he spoke clearly of his purpose:

Jesus replied, "The hour has come for the Son of Man to be glorified…Now my heart is troubled, and what shall I say? 'Father, save me from this hour'? No, it was for this very reason I came to this hour. Father, glorify your name!" Then a voice came from heaven, "I have glorified it, and will glorify it again. (Jn 12:23, 27-29)

And later, at the last supper with his disciples, just before his arrest and crucifixion:

After Jesus said this, he looked toward heaven and prayed: "Father, the time has come. Glorify your Son, that your Son may glorify you. For you granted him authority over all people that he might give eternal life to all those you have given him. Now this is eternal life: that they may know you, the only true God, and Jesus Christ, whom you have sent. I have brought you glory on earth by completing the work you gave me to do. And now, Father, glorify me in your presence with the glory I had with you before the world began. (Jn 17:1-4)

Christ's ultimate purpose is to glorify God. The ultimate purpose of the incarnation, of the miracles, of suffering and dying on the cross, and of rising again to life and ascending into heaven, the ultimate purpose of every work of Christ is to glorify God (Father and Son).  God's greatest purpose then is to demonstrate his glory to all of his creation.  If this conclusion is correct then God's greatest commandment must directly contribute to his greatest purpose.  Loving God must be the best way that we can glorify God.  In fact it must be a prerequisite for everything else we purposefully do to glorify God. 

1 Corinthians 13 "If I speak in the tongues of men and of angels, but have not love, I am only a resounding gong or a clanging cymbal. 2If I have the gift of prophecy and can fathom all mysteries and all knowledge, and if I have a faith that can move mountains, but have not love, I am nothing. If I give all I possess to the poor and surrender my body to the flames, but have not love, I gain nothing."

Paul is not talking only about love for others.  He makes that clear with his concluding sentence in verse 13, "And now these three remain: faith, hope and love. But the greatest of these is love."   Our faith and hope are placed in God, so also is the greatest of these three, "love."
Loving God with all of our heart, soul and mind necessarily means that he is the source of our deepest joy. Owen sums up how we can best live for God:

We live unto God as our Lord, when our principal aim is to enjoy him as our chief good." John Owen, Sermon XII. Enoch’s Walk with God.

So, enjoy!