1 Nephi 13

In this chapter (and earlier), Nephi sees the eventual decline and destruction of his descendants. In verse 35, the Lord says that he will visit the Nephites and that they will write many precious things. After they have been destroyed, these precious things will be hidden and shall come forth at a later time for the remnant of the seed of the Nephites and Lamanites. I always assumed that what we have in the beginning of the Book of Mormon was written for the benefit of the Nephites, where the later things are for our day. After all, by the time Mormon and Moroni were writing, there were no righteous left to even read what they were writing. I still think that this is true, to an extent, but after reading this verse, I think that when Jacob, Enos, etc. say "and on these plates it was commanded I write the things of God", perhaps that was because Nephi knew what they would be used for. I imagine he was sad as he wrote, but also hopeful that the things he wrote would later save his great-great-many great-grandchildren.