What are we to understand from these words spoken by Elder Maxwell in his talk “God Will Yet Reveal” when he said, “We would not even know of the impending third witness for Christ except through the precious Book of Mormon, the second witness for Christ! This third set of sacred records will thus complete a triad of truth.”
Back in 1986, Elder Maxwell gave the talk you mentioned, God Will Yet Reveal. Elder Maxwell recognizes the spiritual bounty that comes into our lives by having the words of prophets – not just living prophets, but the dead as well. They extend “mankind’s spiritual memory”. Living in the dispensation of the fulness of time, we are privileged to have the precious treasure that is the scriptures. In his words, “without this precious, spiritual perspective, the human family is seldom more than one generation away from deep doubt and even disbelief”. The quote you have given is best understood from the talk itself.
“Lost books are among the treasures yet to come forth. Over twenty of these are mentioned in the existing scriptures. Perhaps most startling and voluminous will be the records of the lost tribes of Israel (see 2 Ne. 29:13). We would not even know of the impending third witness for Christ except through the precious Book of Mormon, the second witness for Christ! This third set of sacred records will thus complete a triad of truth. Then, just as the Perfect Shepherd has said, “My word also shall be gathered in one” (2 Ne. 29:14). There will be “one fold and one shepherd” (1 Ne. 22:25) in a welding together of all the Christian dispensations of human history (see D&C 128:18).“
Nephi testified (in the 2 Nephi verses referenced above) that The Book of Mormon would come forth prior to the gathering in and reclaiming of the Lehites. He then testified that a similar process would happen with the other lost tribes.
“And it shall come to pass that the Jews shall have the words of the Nephites, and the Nephites shall have the words of the Jews; and the Nephites and the Jews shall have the words of the lost tribes of Israel; and the lost tribes of Israel shall have the words of the Nephites and the Jews.
“And it shall come to pass that my people, which are of the house of Israel, shall be gathered home unto the lands of their possessions; and my word also shall be gathered in one. And I will show unto them that fight against my word and against my people, who are of the house of Israel, that I am God, and that I covenanted with Abraham that I would remember his seed forever.“
How great is our day! We have the record of two covenant peoples of the Lord! We have the witnesses of His dealings with two nations! And how much greater shall the future day be! The poet W. W. Phelps states it thusly (in The Spirit of God as sung at the Kirtland Temple dedication):
“Old Israel that fled from the world for his freedom,
Must come with the cloud and the pillar, amain:
And Moses, and Aaron, and Joshua lead him,
And feed him on manna from heaven again.“
Like The Book of Mormon, lost Israel’s records will come forth preparatory to the Second Coming of Christ. Like the gathering of the Lehites (returning them to the covenants the Lord made to their fathers), scattered Israel will be gathered home to the lands promised their fathers and worthily inherit the long-awaited blessings. These are days never to be forgotten!