Jesus has already stated that the purpose of his ministry was in no way to destroy the Law and the prophets (that is, the Old Testament) but to fulfill them.

In this passage he begins to flesh out what that means. He seeks to bring the Old Testament law and teaching into its fulfillment by expounding its inner intent and purpose for the people of his own day. In “fulfilling” the law, he fills it up with meaning, demonstrating how it reveals to us the will and purpose of God.