These verses contain what are commonly known as the “theme” of the Sermon on the Mount. In these verses, the Matthean Jesus makes explicit that he is a law abiding Jew. His attitude towards the Jewish law is fundamentally positive. However, Jesus also makes explicit here, that he has come not merely to confirm or establish the law, but to fulfil or complete it. This means that he will go beyond a purely legal interpretation to a broader perspective. He will remove the focus from the mere external and concentrate on the internal. The focus will be more on the attitude than merely on the action.
While laws, rules and regulations are necessary and help towards order, it is also possible that they can become ends in themselves and not as they are meant to be, means to an end. We might follow in some cases the letter of the law, but miss out on its spirit. We might even follow the rule or law only because we are afraid of getting caught and punished and not because we are convinced of it.