These few verses give us great reason to read and understand the Old Testament, the Law that was provided by God (as opposed to that which the Pharisees had created). Jesus defines a point in history that is before and after John the Baptist:
Until John the Baptist, the law of Moses and the messages of the prophets were your guides. But now the Good News of the Kingdom of God is preached, and everyone is eager to get in. (NLT)
People are eager to hear the Gospel, they really are! Perhaps we make it too difficult, too complex or maybe we make it too simple, too cheap!! Somewhere between the two ends of the spectrum we need to preach the Gospel and let the Holy Spirit do his great work. We don’t have to have all the answers or even pretend to understand all that is before us. What we know is that Jesus came to fulfill all we read about in the Scriptures and we must share that as faithful witnesses.
The Law will not disappear. Adultery is still adultery, yet another reference that points to the sanctity of marriage (that’s a whole different subject). God provided a firm foundation in the old covenant and Jesus builds the church on top of this unmovable force.