3 Nephi has been referred to as the Holy of Holies of the Book of Mormon, and in important ways chapters 18 and 19 are the heart of 3 Nephi, for in these two chapters, the Nephites entered into a new covenantal relationship personally with the Lord. In a way, chapters 18 and 19 can be thought of as the Ark of the Covenant at the very center of the Holy of Holies. There the people enter into a covenant with the Father. And then they pray to the Father, and they see Jesus Christ as the Great High Priest offering prayers of intercession and blessing.
In ancient Israel, the High Priest went into the Holy of Holies in the Temple in Jerusalem only on the most sacred of days, bringing about purity and eternal blessings for all who would obey and be faithful. That was the peak of Hebrew worship, and a similar, more literal experience stands here at the zenith of the Book of Mormon.
3 Nephi, as a spiritual gem and model of purifying preparation, “contains those matters that the Savior himself felt were and are most important to the functioning of his church and absolutely essential for sons and daughters of God to internalize if they want to be exalted.” As I see it, “The book of 3 Nephi lays forth a holy template for how one may dwell forever in the house of the Lord Jesus Christ, the Son of God and the great and eternal High Priest of all mankind.”
Book of Mormon Central, “Why Has 3 Nephi Been Called the Crown Jewel of the Book of Mormon? (3 Nephi 17:17), KnoWhy 210 (October 17, 2016).
John W. Welch, “Seeing Third Nephi as the Holy of Holies of the Book of Mormon,” Journal of the Book of Mormon and Other Restoration Scripture 19, no. 1 (2010): 36–55.
Andrew C. Skinner, Third Nephi: The Fifth Gospel (Springville, UT: Cedar Fort, 2012).