The introductory “wherefore” of verse 18 is grammatically dependent upon the last clause of verse 17 “Wherefore, he will proceed to do a marvelous work and a wonder among the children of men.” One of the events of the conceptual end is the “marvelous work and a wonder,” which becomes defined by Nephi’s declaration that “he shall bring forth his words unto them.”
The grammatical referent for “he” returns to “the Lord” at the beginning of verse 17. Thus the marvelous work and a wonder will be when the Lord brings his words to future Israel. How is this to be done? Certainly Israel has had copies of the Lord’s words for centuries. The particular words that will come, however, will be “given them for the purpose of convincing them of the true Messiah.” This purpose in the words to be given future Israel narrow the candidate texts to the New Testament and the Book of Mormon. Because Nephi specifically relates these words to a time near the end, it is the Book of Mormon to which he refers, and in a more immediate context, his own testimony. Nephi understands that his personal witness of the Messiah will be given to the future Israel as a means of convincing them of the Messiah that Nephi has come to know so well and of whom he bears strong witness.
Nephi specifically notes that there is only one Messiah. His reason for being so specific must be his future vision in which other candidate “messiahs” would be proposed. We need not suppose that these proposed messiahs would be evil in intent nor that the deception of which Nephi speaks is malicious in intent. There have been great leaders among the Jewish people who have bee proposed by the people of the land (the Macabeean revolt) or by their congregation (some modern Jewish sects). That the leadership qualities of such men should inspire hope is understandable. That they are not the expected Messiah is certain.
Narrative: The introduction of this purpose of the Book of Mormon as a testimony of Jesus begins to shift the focus of Nephi’s discourse. Where he begins with a specific reference to Isaiah, it is the his testimony of Jesus as Messiah that becomes the main point of much of his text. Of course there were Messianic references in Isaiah, but the critical launching point from Isaiah to Nephi was the restoration of Israel. It was this prophecy of the future redemption of Israel that becomes Nephi’s reason for his own prophecy of those later times and events. The mission of the earthly Messiah fits into to that context, but the Messiah so firmly occupies Nephi’s thoughts as to shanghai the logical development of his narrative. Once begun, his testimony of the Messiah becomes the dominant theme of his discourse, and only tangentially returns to either Isaiah or the restoration of his people.