At least four thousand years ago, the brother of Jared saw all the inhabitants of the earth. As we learned earlier from the original writings of Isaiah, this vision was recorded in the sealed portion of the plates given to Joseph Smith and were never translated by him. They contain “a revelation from the beginning of the world to the end thereof” (2 Nephi 27:7; JST, Isaiah 29:11–12). The reason for their not being translated until after the time “that [Christ] shall glorify [his] name in the flesh” (Ether 3:21) was because “they shall not be delivered in the day of wickedness and abominations of the people” (2 Nephi 27:8; JST, Isaiah 29:13). When they do come forth during the Savior’s millennial reign, they will prove conclusively that Jesus Christ is an omniscient God, knowing the end from the beginning of mankind both individually and collectively.
When the brother of Jared came unto Christ (Ether 3:22) is not made clear. Although it could imply it was written after the brother of Jared’s death, or after his translation (see Ether 13:34), the vision was given sometime after the Lord was speaking to him on the occasion of his first appearing to him (Ether 3:25). It must be remembered that Moroni is abridging the record of Ether, or the Jaredite records, and is making a general statement about what happened to the brother of Jared following his personally seeing Christ (vv. 17–25). The Lord saying “unto him in times before, that if he would believe in him that he could show unto him all things” (v. 26) clearly indicates the vision of all the inhabitants of the earth was given after the initial appearance of Jesus Christ (v. 13 above).
The language that could not be read (v. 22) has been suggested to be the Adamic language. We know that it was a language that could not be read, and the Lord had confounded it (vv. 23–24). If the language spoken prior to the building of the tower of Babel, or the great tower (Genesis 11:1–9; Ether 1:3), was the Adamic language, it would be the language in which the brother of Jared wrote. Therefore, this seems to be the language in which it was written. We do know the language was translated into the Nephite language by King Mosiah through the means of the Urim and Thummim (see Mosiah 28:11–27). The Urim and Thummim was the two stones that would magnify the things the brother of Jared would write (Ether 3:24). The same “Urim and Thummim which were given to the brother of Jared upon the mount, when he talked with the Lord face to face” was given to the Prophet Joseph Smith to translate the Book of Mormon (D&C 17:1, 6). The two stones were sealed up with the brother of Jared’s records (vv. 27–28).