The command to love God with all of our being, when seen apart from the gospel, is a demanding law that breaks our spirit. When we are being honest we know that we naturally love self more than anyone/anything else, so a command we cannot keep (love God first) does not offer life, but only condemnation. And any religion that offers life through our own obedience or affection is sure to disappoint and ultimately produce despair. This led Martin Luther, before his conversion, to responded to the law seen apart from the gospel by saying, "Love God? Sometimes I hate Him!" But love is not just the command of God. It is also the root and the fruit of the gospel.
The Command of God
Yes, love is the command of God. It is a central part of God's character and the essence of his will for his people. When asked what the gratest commandment is, Jesus replied, "You shall love the Lord your God with all your heart and with all your soul and with all your mind. This is the great and first commandment. And a second is like it: You shall love your neighbor as yourself. On these two commandments depend all the Law and the Prophets." This is what God wants for and from us. But here we fail, for we do not love as we should. Thankfully love is not only the command of God.
The Root of the Gospel
Love is also the root of the Gospel. God's love is demonstrated toward us in that while we were still sinners, Christ died for us. It was love that moved the Father to send the Son. And it was love that moved to Son to offer himself as our sacrifice. Jesus said, "Greater love has no one than this, that someone lay down his life for his friends. You are my friends..."
The Fruit of the Gospel
And here is grace upon grace. Love experienced as the root of the gospel then becomes love expressed as the fruit of the gospel. The promise of God is that he gives his people new hearts; hearts that beat with love for him and others. It's not just that we learn love from the example of Jesus (which we do), but also that God's saving love for his people truly changes us. This is real love. Not that we loved God, but that he first loved us and sent his Son to die for us. We love, because he loved us. And we grow in love through the ministry of his Spirit which dwells in us. This love, as the fruit of the gospel, is the heart of godliness.
Love God? I used to hate him! But he loves me, and saved me from such hate so that I do love him, though imperfectly. And, through Jesus I am not only the object of his love, but also the instrument of his love.