My wife and I were reflecting upon the 10 Commandments and Jesus' "greatest commandment" a few days ago. The reflection follows closely in line with my previous post, and may shed some additional light upon those thoughts.
Check out Matthew 22:34-40 -
When the Pharisees heard that he had silenced the Sadducees, they gathered together, and one of them [a scholar of the law] tested him by asking, “Teacher, which commandment in the law is the greatest?” He said to him, “You shall love the Lord, your God, with all your heart, with all your soul, and with all your mind. This is the greatest and the first commandment. The second is like it: You shall love your neighbor as yourself. The whole law and the prophets depend on these two commandments.”
Note that Jesus sums up the first 3 commandments in one sentence, and the 7 remaining commandments with "You shall love your neighbor as yourself."
The 10 Commandments, many of which begin in the negative (Thou shalt not), are necessary to achieve a freedom from sin. Following the law achieves this. But, Jesus is proposing something greater than the moralism that had become of the "law and the prophets."
He begins by cutting to the heart of what it means to be human - "You shall love." Do what you were created to do!
Here, Jesus answers the "why?" surrounding the 10 Commandments. Why deal with all of these negative commands? For the positive reason that you were created to love God (which is a proper response for all that is given), neighbor and self. You were called to love the gift that is your life - perfect love casts out all fear. Indeed, this requires the purgation and freeing yourself from sin through grace, but it makes so much more sense, and is much more meaningful in the positive light.
Jesus' response in the Gospel of Matthew pushes us to the proper place before the commandments - a place in which we have an answer to the "why?" behind the law. For this reason, I often quote Pope Benedict XVI in the beginning of his first encyclical Deus Caritas Est:
"We have come to believe in God's love: in these words the Christian can express the fundamental decision of his life. Being Christian is not the result of an ethical choice or a lofty idea, but the encounter with an event, a person, which gives life a new horizon and a decisive direction."
It is within the encounter, within the new relationship of the human heart with Christ that the freedom for life leads the conversion from sin. Without the relationship, the commandments seem limiting, negative and difficult.