Mormon adds his apostolic testimony to that of Nephi. Although this passage is written to his future readers, the Gentiles, he refers to them in third person as “they” (“this” is the Book of Mormon). In this context, modern Latter-day Saints are Gentiles. Mormon recapitulates the Savior’s message that it “is expedient that they [the Gentiles] should have” the Book of Mormon “first.” From them, it will go to the house of Israel, including Lehi’s descendants.
Mormon specifies that the Book of Mormon’s coming forth will “try their faith.” This phrase is best interpreted in the light of the Psalm 66:10: “For thou, O God, hast proved us: thou hast tried us, as silver is tried.” (See commentary accompanying 3 Nephi 13:14–15.) It does not have the modern connotation of being an intentional attempt to damage faith by providing a difficult test. When our faith is “tried” like silver being purified by the refiner’s fire, means that adversities and challenges exist to polish and purify our faith, not to risk our losing it.
The promise is that, if the Gentiles’ faith is refined according to plan, “then shall the greater things be made manifest unto them.” In parallel fashion, their lack of faith means that “the greater things [shall] be withheld from them.” This is the same promise that the Lord makes to all of his children. To those faithful in a few things, greater things will be added.
This is the focus of the parable of the talents (Matt. 25:14–28). The two successful stewards received an increase. The fearful steward who preserved only what he had been given lost it. This promise of greater things certainly applied to Joseph Smith as the translator of Mormon’s record. The restoration that followed Joseph’s faithfulness in translating the Book of Mormon is part of many “greater things” given after the Book of Mormon’s coming forth.