See Genesis 48:19–20; Deuteronomy 33:13–17; Jeremiah 31:6–9; and Revelation, 3 Nov. 1831 [D&C 133:30–34].
Daniel 2:44. Japheth was traditionally considered the ancestor of the Gentiles.
The Book of Mormon states that Gentiles “shall assist my people, the rem[n]ant of Jacob; and also, as many of the house of Israel as shall come, that they may build a city, which shall be called the New Jerusalem.” (Book of Mormon, 1830 ed., 501 [3 Nephi 21:23].)
See Revelation, 20 July 1831 [D&C 57:1–3]; and Revelation, 22–23 Sept. 1832 [D&C 84:2–5].