These verses will serve as a transition from the command to write in the context of the coming forth of the Book of Mormon to the specific future role of these twelve. The Book of Mormon will come forth, and it is a written text. The Savior has prophesied that it will come forth.
Now the emphasis is not on the position of the Book of Mormon as harbinger of the end times, but as part of the law against which mankind will be judged. The scriptures harbor the words and the will of God, therefore we may be judged by how well we live by the words and will of God as found in our scriptures. This encompasses not only the Book of Mormon that his the touchstone writing of this verse, but all scriptures. This includes the brass plates, but for us it includes the whole of the Bible, and the Doctrine and Covenants and the Pearl of Great Price.
[all things are written by the Father]: Obviously, none of the scriptures has been literally written by the Father. However, because the Father is the source of the revelations that become the scriptures; is the source of the inspiration that becomes the scriptures, it may be said that the Father “wrote” them by extension. Thus we are judged out of the books because they contain the will and words of the Father.
Reference: Similar language is found in the book of Revelation:
Revelation 20:12
12 And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works.
While the language is similar, the metaphorical context is different. In Revelation the book is never physical, but symbolic. The book of life is a metaphor of Godly knowledge and understanding of our actions and our hearts. There is no indication in the book of Revelation that this judging according to the book of life has anything to do with a physical book.
In the 3 Nephi context, the language may be similar, but the meaning is clearly connected to scripture, which has been a theme of the Savior’s visit. Thus the context in the Book of Mormon is consistent with all the rest of the meaning of the Savior’s discourses. While the language may have similarities to that of Revelation, the meaning and context differ significantly.