Nephi knows that records serve multiple purposes. The first is the preservation of “language,” perhaps meaning culture and a knowledge of God. (See commentary accompanying 1 Nephi 1:2–3.) Another is recording an official history. Yet another is a persuasive document that will convince the reader of Yahweh’s goodness. Nephi dedicates the small plates to this last task.
In light of Nephi’s declaration that he did not want to repeat Lehi’s record nor the genealogies, why did he include large sections of Isaiah? Like the genealogies of Joseph, Isaiah’s prophecies were certainly available on the brass plates, as evidenced by their quotation throughout the Book of Mormon. Although Nephi never says so, no other described source is available for the Isaiah material. Thus, Nephi did not decide to include or exclude text based on whether it was available elsewhere (both Lehi and Isaiah were available on other plates) nor on the space available on the plates (writing room becomes an issue in Omni, but not earlier, since Nephi could, presumably, have made more sheets if he had wished to do so.) Rather, Nephi found important meaning in Isaiah, meaning that will be discussed in the commentary accompanying the Isaiah passages.
Culture: Chris B. Hartshorn, a high priest in the Reorganized Church of Jesus Christ of Latter Day Saints (now Community of Christ) and editor of the Saints’ Herald, notes of the phrase “the God of Abraham, and the God of Isaac, and the God of Jacob”: “This is no play on words. It was to distinguish their God from the tribal gods of the heathen nations around them. The scriptural background for this expression is an announcement to Moses as he gazed on the burning bush (Ex. 3:6).”