“I bless you with increased understanding of the Book of Mormon. I promise you that from this moment forward, if we will daily sup from its pages and abide by its precepts, God will pour out upon each child of Zion and the Church a blessing hitherto unknown—and we will plead to the Lord that He will begin to lift the condemnation—the scourge and judgment. Of this I bear solemn witness.”
A keystone is the central stone in an arch. It holds all the other stones in place, and if removed, the arch crumbles.
… Just as the arch crumbles if the keystone is removed, so does all the Church stand or fall with the truthfulness of the Book of Mormon. The enemies of the Church understand this clearly. This is why they go to such great lengths to try to disprove the Book of Mormon, for if it can be discredited, the Prophet Joseph Smith goes with it. So does our claim to priesthood keys, and revelation, and the restored Church. But in like manner, if the Book of Mormon be true—and millions have now testified that they have the witness of the Spirit that it is indeed true—then one must accept the claims of the Restoration and all that accompanies it.
Excerpts taken from Teachings of Presidents of the Church: Ezra Taft Benson, Chapter 9.