The next part of the discourse deals with the question of what it meant for the law to be fulfilled. These were people who had lived the law of Moses, and traced their living of that law back to the Old World. How does something that old and respected change, and what does it mean to say that it is fulfilled?
Christ reiterated the phrase from the Sermon at the Temple that he did not come to destroy the prophets (3 Nephi 12:17). He was not changing everything that the prophets had said. They taught truth, and truth remained.
However, there is a distinction, and there is something new. Before discussing what is new, he reiterated the important part of what would be retained from that which was old: “The covenant which I have made with my people is not all fulfilled; but the law which was given unto Moses hath an end in me.”