Jesus informed the Nephite audience that the Father had commanded him to give them those prophecies that were not contained in their scriptures “that they should be given unto future generations.”
Using the words of Isaiah and Malachi as his preface, the Savior then proceeded to expound “all things” to the people—from the beginning through the winding-up scenes of the world’s mortal existence. Mormon included an abridged account for a “lesser part” of Jesus’ teachings, which we have in the Book of Mormon.
The Savior’s teachings were so extensive that “a hundredth part” of them could not even he recorded in the Book of Mormon (compare Words of Mormon 1:5; 3 Nephi 5:8-11). This statement of Mormon’s reminds us that what we have is merely an abridgment of many volumes of records kept throughout Nephite history.