Moroni had been speaking to the Lamanites. He now speaks to the whole world who will sometime in the latter days receive the opportunity to accept or reject the Book of Mormon. It was to go to “every nation, and kindred, and tongue, and people” (Revelation 14:6). Moroni may or may not have known that he would be supervising that work as an angelic being. The Lord seems to have Moroni in mind when he says:
36 And now, verily saith the Lord, that these things might be known among you, O inhabitants of the earth, I have sent forth mine angel flying through the midst of heaven, having the everlasting gospel, who hath appeared unto some and hath committed it unto man, who shall appear unto many that dwell on the earth.
37 And this gospel shall be preached unto every nation, and kindred, and tongue, and people. [D&C 133:36–37]
Through faith, the power of God would bring about the restoration of the gospel in the latter days. Through hope, people would do good works (Moroni 10:25). Those who reject the work of God because of unbelief and iniquity will die in their sins and not be saved in the kingdom of God (10:26). Moroni’s declaration was according to the word of God.
Moroni’s tenth requirement, that may be a reason for not receiving a witness of the Holy Ghost that the Book of Mormon is true, is to recognize that the coming forth of that book is fulfillment of prophecy (v. 28). Moroni prophesied that his words would be like one crying from the dead, and as speaking out of the dust (v. 27). Isaiah had prophesied that the Book of Mormon would come forth in this manner Isaiah (29:4). A brief review of a few other prophecies of the coming forth of the Book of Mormon would include, but not be limited to, the following: Ezekiel 37:15–20, the stick of Joseph (the Book of Mormon) becoming one with the stick of Judah (the Bible); Psalm 85:10–11, truth speaking out of the ground; John 10:14–16, other sheep not of this fold; Revelation 14:6–7, and another angel with the everlasting gospel. The promise of God showing unto the latter-day reader that what Moroni had written was true (Moroni 10:29) could come in many ways, but was probably referring to the three witnesses and the eight.