Q: What is the sum of the ten commandments?
A: The sum of the ten commandments is to love the Lord our God with all our hearts, with all our soul, with all our strength, and with all our mind; and our neighbor as ourselves.
Matthew 22:37-40: And he said to him, "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."
I'm certainly thankful for how Jesus Christ summarizes the law for us here in Matthew 22. Remember the context of this passage. First the Sadducees came to Christ hoping to ensnare him over the idea of the resurrection of the dead. The Sadducees only accepted the first five books of the Bible as Holy Scripture, and because these books make, in their understanding, no direct reference to the resurrection of the dead, the Sadducees rejected the idea of the resurrection. So Christ, in his response to them, quotes Exodus 3:6 by saying, "Have you not read what was said to you by God: 'I am the God of Abraham, and the God of Isaac, and the God of Jacob'? He is not God of the dead, but of the living." This response effectively silenced the Sadducees, and now the Pharisees want their turn at trying to ensnare Jesus. This all comes from an attempt at making Jesus look like a false teacher by entangling him in his words (Matt. 22:15). Which commandment in the whole law is the most important, the Pharisees asked him backhandedly. Christ's response here is beautiful. Instead of picking one commandment, he summarizes the first four commandments, "You shall love the Lord your God with all your heart and with all your soul and with all your mind." This is exactly what the first four commandments teach us. They teach us how to worship and glorify God. Think about it. You shall put no other gods before the one true God, you shall not build idols or make graven images of God, you shall not take the Lord's name in vain, and you shall keep the Sabbath holy. These commandments instruct us on our attitude and posture towards God.
But Christ doesn't stop there. He then effectively summarizes the second six commandments, "You shall love your neighbor as yourself." By doing this, he is showing that the commandments are all interrelated. Part of loving God with all our hearts and with all our souls and with all our minds includes loving our neighbors (which includes our enemies) as ourselves. The ten commandments can't be separated. It's, as we said before, a complete summary of the law of God. At it's most basic level, the question of the Pharisee is dubious because it is trying to get Christ, in essence, to quantify God's law. All of God's commands are related to one another, all of them teach us and instruct us how to live lives that bring glory and honor to God. None of God's commands are to be dismissed as a "lesser command". This is why Christ's summary is so helpful to us. He takes the ten commandments and summarizes them succinctly so that we can see and understand the very heart of God's commandments, and what role they are to play in our lives as we seek to live in a way that glorifies and honors him.