Obeying the law
Jesus was questioned many times about the Old Testament law and whether or not it should be followed. He became quite adept at crafting answers to these questions that neither refuted the law nor supported the notion that obedience to the law provided salvation. In most cases, these questions were not legitimate, but rather traps set to twist His words into something that would be punishable by the authorities.
Jesus' statement here is an important one for keeping the law in its proper perspective. While the Pharisees treated the law as if it was God Himself, Jesus provides a subtle reminder here that the law only became necessary when sin entered the picture after the fall of Adam and Eve. At that point, we began to divert from what we were created to be. We were created in His image and with His nature. Had we stayed there, the law would be completely unnecessary. We would naturally do those things prescribed by the law because it would flow naturally from our hearts. That's how it works with God. He hasn't placed Himself under the law because there is no need to do so.
As Jesus said, if our hearts had not become hardened, the law would be completely unnecessary. We are where we are, though, so the law came into being. But strict obedience to a set of laws is not the goal or the answer. Knowing the nature of God and asking Him to draw us closer to Him allows us to move closer to who we were created to be- people in His image who naturally do things from the heart that might otherwise require laws to bring about. The focus is heart transformation and redemption by the Holy Spirit, not behavior modification through adherance to a set of laws. Pray that the Holy Spirit will differentiate the two for us.