Hear, O Israel: The Lord our God, the Lord is one. You shall love the Lord your God with all your heart and with all your soul and with all your might.
Deuteronomy 6 contains the heart of the covenant between God and his people. The Lord our God, the Lord is one. He is not one god among many gods. Nor is he the chief god. He is alone the only God. The command that follows, “You shall love the Lord your God…” is central because the whole book is concerned with the renewing of the covenant with God, and although the renewal demanded obedience, that obedience would be possible only when it was a response of love to the God who had brought the people out of Egypt and was leading them into the promised land.
In John 5, Jesus called his listeners out on their neglect and blindness to the testimony of the Scriptures, “In them you think you have life.” He said, “But I know that you do not have the love of God within you.” He recalls this foundational command to love God with all your heart and soul and might. It is on this point that they had missed it. They had received the law of love and turned it into a matter of pride. It was a set of rules they could keep to be better or more favored than those around them.
This is certainly a danger that we need to be very mindful of, especially as we grow in our understanding, our liturgy, and our singing of Psalms and hymns. All of this is only for the purpose of drawing in closer to God, to love him for himself and to love our neighbor who is made in the very image of God.