These final two paragraphs which conclude the book of Third Nephi are instructions to the Gentiles of America from the Lord Jesus Christ.
The Lord knew how wicked the Gentiles of America would have become by the time the Book of Mormon and the restoration of the gospel got under way. Therefore, the Lord instructed Mormon to give them a warning and a commandment.
This segment of the Book of Mormon begins with a complete surprise. Suddenly we are in the administration of the sonof Nephi III. But what happened to his father? When did Nephi IV take over as historian and leader of the Church? When were the records and all the Nephite memorabilia turned over to him? The record is silent.
Perhaps this is for a good reason. Mormon had been told not to record the names of the three Nephites and it is highly possible that they had included Nephi III. It is even possible that another one was his brother, Timothy, whom Nephi had raised from the dead. A third disciple who could have qualified for this high assignment was Timothy's son, Jonas. Because they were all of one family, it may have been a prudent reason not to have named them. In 3 Nephi 19:4, Mormon lists these three men as the first of the disciples and this may be significant since Mormon had been administered to by the Three Nephites and knew who they were.1 Now let us turn to the single chapter in the writings of Nephi IV.
This last verse was the sublime achievement which all of the Nephite prophets had longed to achieve. The supreme attainment in the days of Nephi IV was the fact that universal conversion of all the people included both Nephite and Lamanites. A portrayal of the massive conversion of all the people is shown in volume four of Treasures from the Book of Mormon on page 113.