Nephi's commentary on Isaiah concludes with accelerating insight into why Isaiah appears as a part of his record. In 2 Nephi 31: 1, he makes this significant statement: "I, Nephi, make an end of my prophesying unto you, my beloved brethren. And I cannot write but a few things, which I know must surely come to pass; neither can I write but a few of the words of my brother Jacob." (Emphasis added.) He knows these things are going to happen, because through the power of God he has seen them.
Nephi taught his brother, Jacob, about these truths. Jacob, in turn, was consecrated by Nephi as a priest. Jacob knows about them not only through Nephi's teachings, but because he, too, had an audience with Christ. The similarities between Nephi and Jacob on this are striking. First, in Jacob's sermon recorded by Nephi, Jacob uses an extended quote from Isaiah to support his teachings. The reference to the "words of my brother Jacob" is, by and large, a reference to Jacob's extended quotation of Isaiah in the Second Nephi materials. If Nephi could only include "but few of the words of my brother Jacob," it should make us take serious thought when the overwhelming majority of those words are Jacob quoting Isaiah. Second, when Jacob succeeds Nephi and writes his own record on the Plates of Nephi, Jacob's book follows Nephi's pattern of quoting extensively from an earlier prophet. Jacob quotes from Zenos rather than Isaiah. His quote constitutes the single longest chapter in the Book of Mormon. Just like the Isaiah materials, this quote from Zenos deals with the unfolding history of Israel, a latter-day restoration of the covenant, and the propensity of Israel to deviate from the path. Jacob, like Nephi, wrote his portion of the record with later generations (including ourselves) in mind.