Nephi’s probable intended conclusion to the story of Lehi blessing his children is found in the first phrase of verse 14: “For I, Nephi, was constrained to speak unto them, according to his word; for I had spoken many things unto them, and also my father, before his death.” When Nephi wrote that, however, he began to think on the task of writing, and he moves from his intended outline into a spontaneous addition to his text, similar to what we saw in the commentary on 1 Nephi 19:5–6, where Nephi similarly departed from his outline, based on what he had just written that triggered the aside.
In this case, he notes that many of the things that Lehi spoke were written on his other set of plates, the ones we call the large plates of Nephi. That note triggers Nephi to think on the division of the plates, something he has already discussed in 1 Nephi 9 and 1 Nephi 19. Both of those occasions were also asides inserted into the planned text. Both of those also emphasized the sacred purpose of the small plates, and that happens again here.
Nephi reiterates that upon the small plates he writes the things of his soul. As he ponders the things which mean the most to him, it will lead to the spontaneously poetic expressions that close out this chapter.