Nephi’s overall purpose was to convince his own people to “remember the Lord their Redeemer” (v. 18), but he spoke to all the house of Israel because he knew by the Spirit that his writings would go to all of them. He had been shown the inhabitants of Jerusalem the same as had been seen by the prophets of old (vv. 19–20). However, not all of the prophets had been shown the Nephites (v. 21). Isaiah was one of the prophets who had been shown the future destiny of both the Jews and the people of Lehi. Wherefore, Nephi recorded one of his prophecies of the Jews (Isaiah 48; 1 Nephi 20); and one of his prophecies concerning the people of Lehi (Isaiah 49; 1 Nephi 21). His prophecies were written on the plates of brass, the source used by Nephi.
The Bible confirms, but the references are too numerous to be included here, that the prophets of old were shown many revelations concerning the Jews. Some of the many prophets, besides Isaiah, who prophesied extensively of the Nephites, and who were shown the people of Lehi, would include Jacob the father of the house of Israel (Genesis 49:22–26); Moses (Deuteronomy 33:13–17); Ezekiel (37:15– 28; 17:22–23); and King David (Psalm 85:10–11). As discussed above, Zenos’s prophecies of the remnant of Joseph were once on the plates of brass.