Nephi provides a prophetic interlude between the words of Jacob and into the words of Isaiah, and explains why he has included both of these accounts into his record at this point.
Namely, Nephi has chosen the words of these two because they both have seen the Savior, “even as I have seen him.” Nephi’s ultimate purpose in his writing is to establish the truth of his teaching regarding the son of God and his coming.
He notes that his “soul delighteth in proving unto my people the truth of the coming of Christ.” Presumably, an extended family coming from Jerusalem would have had varying sentiments about the coming of the savior. Even among those who followed Nephi, it would not be surprising to have found many reverting to older beliefs and growing doubtful regarding Christ. Thus, Nephi emphasizes the importance of Christ’s coming and his “soul delighteth in proving unto my people that save Christ should come all men must perish.”
Nephi also returns to the other themes that I have already noted dominated Jacob’s discourse. Namely, “the covenants of the Lord which he hath made to our fathers” and “his justice, and power, and mercy in the great and eternal plan of deliverance from death.”
Nephi finds in the writing of Isaiah and Jacob kindred spirits, united by their shared visions of the Lord. He thus uses their words to enhance his own, as an added witness.