A young man who recently returned from a mission for the church asked me why the prophecies contained in the Book of Mormon are important for him. He asked, "If the objective of my life is to make my calling and election sure and to receive the Lord in this life, then why should I be concerned about the prophecies in the Book of Mormon? What do they mean to me? How do those prophecies about Gentiles and a remnant of Israel affect me personally finding and coming to Christ?" It's an interesting question. One perhaps we could all benefit by considering.
Joseph Smith said, "The Book of Mormon [is] the most correct of any book on earth, and the keystone of our religion. A man would get nearer to God by abiding by its precepts, than by any other book." For anyone desiring to get "near to God," abiding by the precepts found in the Book of Mormon is a key. One is never nearer to God in this life than when one's calling and election is made sure through the more sure word of prophecy, which is the Lord’s own voice and testimony to a person regarding their assured eternal life. (D&C 131: 5-6) Or, when one succeeds in receiving the second comforter, which is the personal, ministering presence of the Lord by which one is "redeemed from the fall." (John 14: 18-23 and Ether 3: 13) If Joseph Smith is right, (and he is) then abiding the precepts of the Book of Mormon will do more to advance us in the process of finding the Lord’s holy presence than by any other precepts from any other source.
Speaking to the Nephites, the Lord Jesus pointed out the absolute necessity for every person who desires to be a part of His covenant to "believe" His words found in the Book of Mormon. (3Nephi 21: 11)
"Therefore it shall come to pass that whosoever will not believe in my words, who am Jesus Christ, which the Father shall cause him to bring forth unto the Gentiles, and shall give unto him power that he shall bring them forth unto the Gentiles, (it shall be done even as Moses said) they shall be cut off from among my people who are of the covenant."
"Belief" in the words of Jesus Christ that are to be delivered to the Gentiles, (the Book of Mormon,) is required in order to retain a status "among (His) people who are of the covenant." Whosoever will not believe His words in the Book of Mormon will be "cut off" from "among (his) people who are of the covenant." It turns out that "believing" the prophecies in the Book of Mormon that comprise "the words of Jesus Christ that the Father has caused to be brought forth unto the Gentiles," has very much in deed to do with any person receiving the Lord and His covenant.
"Having a testimony" of the truthfulness of the Book of Mormon will do little to bring a person closer to God. Joseph said it would be by "abiding" the book's precepts that we would come closer to God. Precepts that are not known, not understood, not believed, can't possibly be abided by. Generally, the Book of Mormon is much too neglected and ignored (taken lightly according to the Lord (D&C 84: 54, 57)) by latter day saints to be properly abided by. How can words that are not first known, be either believed, or abided by? The words of the Book of Mormon must be intensely searched (2Nephi 9: 51, 2Nephi 31: 20) and carefully considered under the direction of the Holy Ghost. (Moroni 10: 4-5) Then those words must be believed.
Failure to do what is necessary to become intimately familiar with the precepts of the Book of Mormon after it is received is itself failure to believe. The result of such slothfulness will not simply be the delivery of a few halfhearted stripes then a quick introduction into the kingdom of God where it is safe. (2Nephi 28: 8) If the Lord is good for His word, such "unbelief" will result in being "cut off" from among the people of the covenant just as Moses said it would be. (3Nephi 21: 11) The Lord's words are: "whosoever will not believe in my words, who am Jesus Christ...they shall be cut off from among my people who are of the covenant." These are perhaps the very first words we should believe from the Book of Mormon. After all as Nephi said, "the nations who shall possess them (words of the Book of Mormon) shall be judged of them according to the words which are written." (2Nephi 25: 22) Something in all of this behooves us to both "know" and "believe" intimately that which is written in the Book of Mormon.
For example, here are some of the words of Jesus Christ from just one verse of the Book of Mormon that must be "believed" in order to avoid being "cut off" from among the people of the covenant.
"And thus commandeth the Father that I should say unto you: At that day when the Gentiles shall sin against my gospel, and shall reject the fulness of my gospel, and shall be lifted up in the pride of their hearts above all nations, and above all the people of the whole earth, and shall be filled with all manner of lyings, and of deceits, and of mischiefs, and all manner of hypocrisy, and murders, and priestcrafts, and whoredoms, and of secret abominations; and if they shall do all those things, and shall reject the fulness of my gospel, behold, saith the Father, I will bring the fulness of my gospel from among them." (3Nephi 16: 10)
There is a tremendous amount contained in these words of the Lord Jesus Christ that must be "believed" in order to avoid being "cut off from among the people of the covenant." If we break down these words of Jesus to the Nephites, it requires us to believe:
1. The Gentiles will sin against His gospel.
2. The Gentiles will reject the fullness of His gospel.
3. The Gentiles will be lifted up in the pride of their hearts above all the people of the earth.
4. The Gentiles will be filled with all manner of lyings
5. The Gentiles will be filled with all manner of deceits
6. The Gentiles will be filled with all manner of mischiefs
7. The Gentiles will be filled with all manner of hypocrisy
8. The Gentiles will be guilty of all manner of murders
9. The Gentiles will be filled with all manner of priestcrafts
10. The Gentiles will be filled with all manner of whoredoms
11. The Gentiles will be filled with all manner of secret abominations
12. The Father will bring the fullness of His gospel from among the Gentiles.
It would be so much less threatening, it would be so much more comfortable and soothing, to approach this list of condemning prophecies about the Gentiles from the mouth of the Lord with the traditional view of the church that teaches none of these accusations of the Lord have anything to do with the church at all. But that would require "unbelief" of words from the Lord's own mouth. And the resulting promise of being "cut off" from His covenant. Little wonder then, the Lord accused the church of "unbelief" and having taken the precious Book of Mormon "lightly" and placed the church under condemnation as a result. (D&C 84: 54-59)
The Book of Mormon is written in wonderful plain language. We could avoid all of the problems the latter day Gentiles are accused of by the prophets and the Lord in the Book of Mormon by simply believing what the words say. There is no point in, or need to, "transfigure" the holy word of God. (Mormon 8: 33) We should allow the words to mean what they say. The plain and precious words of the Lord in the Book of Mormon say our covenant status depends on us believing what is written. (3Nephi 21: 11) But we don't even believe that. Instead, we believe our baptism and membership in the church assures our covenant status with the Lord regardless of what we do or don't believe from the words of the Book of Mormon.
The Book of Mormon has become largely irrelevant to members of the church. Most members have a favorite verse or two that they quote at the right moment. But mostly the Book is ignored, misunderstood, and not believed. It has been reduced in the minds of most members to a collection of stories, and a few discourses about the first principles and ordinances of the gospel. Nothing more. It would be interesting to know what percentage of members of the church even know there are prophecies concerning Gentiles and a chosen remnant of Israel in the Book of Mormon. The ones that are aware of the prophecies most likely believe the traditional view that "Gentiles" are all "non-members" of the church. In that tradition of their fathers, (D&C 93: 39) "belief" in the words of the Lord Jesus from the Book of Mormon is rendered "unbelief." It is as clear as it can possibly be, unless the holy words are "transfigured," (Mormon 8: 33) that the Gentiles spoken of in the Book of Mormon prophecies are the latter day church established by Joseph Smith. (D&C 109: 60)
It is a deception of the evil one to teach or believe that we can find or maintain a status among the "people of the covenant" while conducting ourselves in "unbelief" of the words of the Lord from the Book of Mormon. The prophecies concerning the Gentiles and the remnant of Israel together with every other word spoken by the Lord in the Book of Mormon must be learned, accepted, and believed. Otherwise we run the risk of being "cut off" from covenant status with the Lord.
So, my young friend, the answer to your question, "what do the prophecies in the Book of Mormon have to do with you making your calling and election sure and finding the presence of the Lord?" Only one thing, EVERYTHING!