1 Nephi 9: The Organization of the Books of Nephi
Nephi makes two sets of records, each bearing his name. Nephi explains that the larger plates will contain a secular history [not pertaining to religion] and the smaller ones will deal primarily with sacred things.
Nephi explains; “…I have received a commandment of the Lord that I should make these plates, for the special purpose that there should be an account engraven of the ministry of my people…. wherefore these plates are for the more part of the ministry; and the other plates are for the more part of the reign of the kings and the wars and contentions of my people.” (1 Nephi 9:3-4)
Nephi tells us that the purpose for writing these plates (other than preserving the record of his people) were not 100% clear to him, however he did these things because the Lord had commanded him to do so; “…for a wise purpose in him, which purpose I know not.” (1 Nephi 9:5)
Today we have these records as part of the Book of Mormon, which God knew would be needed in the Last Days, because He; “…prepareth a way to accomplish all his works among the children of men…” (1 Nephi 9:6)