Verses 14-17 contain the word of the Lord as given to Nephi. What is remarkable is that these words are not found in either 1 Nephi or 2 Nephi. Apparently, Nephi must have recorded this prophecy somewhere else, possibly on the large plates. At any rate, it is important to notice this pattern because it is such a rarity in the Book of Mormon.
In the Bible, this happens all the time. The apostles make reference to all sorts of prophecies that are not extant in our Old Testament. One of the most important is spoken of in Acts, the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began (Acts 3:21). Certainly, a doctrine as important as the restitution of all things is important enough to be found in the Old Testament, but a specific Old Testament prophecy which approximates the words of Acts 3 cannot be found. For more examples, see Lu 1:1, Jn 13:18; 15:25 and Topical Guide, Scriptures, Lost.