Verse 12 concludes Nephi’s chain of arguments. It is more generic than the examples he has used, provides rhetorical closure, and also provides a transition from the examples themselves to the necessity of faith. Nephi’s argument is heavily weighted toward obtaining the brass plates, which involved not only Nephi’s personal miracle and the angel’s appearance, but also proof of the concept that the Lord can provide the means if we provide the faith.
Translation: Nephi’s exhortation to faith is somewhat unusual in Old Testament vocabulary. Faith is more often associated with the New Testament than with the Old. However, faith has never been absent in human experience regardless of the term we might use to define it. In the Old Testament, what we might term faith would be considered loyalty. One was loyal to Yahweh’s cause. As a loyal servant, one would follow Yahweh’s commands. Regardless of the term Nephi might have used, he had learned a significant lesson about faith and includes it in his conclusion. Nevertheless, we must remember that Joseph Smith’s translation was significantly influenced by his Christian and New Testament perspective. Thus, New Testament phrases and vocabularies appear in pre-Christian contexts in the Book of Mormon. Faith was likely one of those terms adopted from the New Testament context.
Verse 13 uses Yahweh’s promise of a land as a motivation for Laman and Lemuel’s obedience. This promise was particularly important for Nephi as he had received personal witness of it (1 Ne. 2:20). See the commentary accompanying 1 Nephi 7:1 for more information on the contrast between Nephi and Lehi’s receipt of the promise.
Variant: In 1837, Joseph Smith changed the phrases: “let us be faithful in to him. And if it so be that we are faithful in to him.” The change appears to replace a more archaic form with a more modern one.