The Sermon on the Mount and its Book of Mormon counterpart in 3 Nephi 12-14 was intended to train missionaries and is referred to as the Savior's missionary training sermon.
The sermon in the Book of Mormon, or the Sermon in Bountiful, has the same setting and purpose as the Sermon on the Mount. Both sermons were given prior to the labor of missionaries and preceded great outpourings of missionary labor which met with powerful success.Missionary work has always been a primary and essential aspect of gospel dispensations, and the dispensation opened by the Savior among the Book of Mormon peoples in the first century A.D. is no exception. - Robert A. Cloward, Institute of Religion instructor in Cedar City, Utah.