How can one believe the Book of Mormon to be scripture when the Bible says we shouldn’t add to the Bible (Revelation 22:18-19)?
Those who level this accusation against the Book of Mormon usually note that Revelation is the last book in the Bible, and conclude that its warning refers to the entire Bible. Actually, the words “the prophecy of this book,” “the book of this prophecy,” and “this book” refer only to the book of Revelation. At the time John recorded those words, the Bible did not exist; there were only separate scrolls for each book. The first bound Bibles did not show up until the fourth century A.D. Some of the earliest Bible manuscripts do not end with the book of Revelation and, in fact, some of them don’t even include that book and omit other New Testament books as well (especially 2-3 John and 2 Peter), while some include books no longer in our Bible (notably Shepherd of Hermas, 1 Clement, Epistle of Barnabas).
Moreover, similar warnings are found in earlier Bible books. For example, in Deuteronomy 4:2, we read, “Ye shall not add unto the word which I command you, neither shall ye diminish ought from it, that ye may keep the commandments of the Lord your God which I command you” (see also Deuteronomy 12:12). Using the same reasoning critics employ against the Book of Mormon, one might conclude from this that only the five books of Moses, the Pentateuch (of which Deuteronomy is the last book), are acceptable scripture, and that we should reject the rest of the Old Testament and all of the New Testament.
The admonition to not add to God’s word is also found in Proverbs 30:5-6: “Every word of God is pure: he is a shield unto them that put their trust in him. Add thou not unto his words, lest he reprove thee, and thou be found a liar.” While mortals are forbidden to add to the divine word, the Lord himself is not bound by such restrictions. To Nephi he declared, “I speak forth my words according to mine own pleasure. And because that I have spoken one word ye need not suppose that I cannot speak another” (2 Nephi 29:9). God’s word is revealed through prophets, and it is through prophets that he has always added to his own word. Thus, we read that, when Jehoiakim, king of Judsah, ordered the burning of Jeremiah’s writings (Jeremiah 36:1-4, 23), the Lord commanded the prophet to restore these words (Jeremiah 36:27-28). “Then took Jeremiah another roll, and gave it to Baruch the scribe, the son of Neriah; who wrote therein from the mouth of Jeremiah all the words of the book which Jehoiakim king of Judah had burned in the fire: and there were added besides unto them many like words” (Jeremiah 36:32).
The incomplete nature of the Bible is demonstrated by the words of the apostle John, author of the book of Revelation and of the book that bears his name: “And there are also many other things which Jesus did, the which, if they should be written every one, I suppose that even the world itself could not contain the books that should be written” (John 21:25).
While mortals are commanded not to tamper with the scriptures, God has no such restriction and can authorize his prophets to write new scripture. “And we know that these things are true and according to the revelations of John, neither adding to, nor diminishing from the prophecy of his book, the holy scriptures, or the revelations of God which shall come hereafter by the gift and power of the Holy Ghost, the voice of God, or the ministering of angels” (D&C 20:35).
“We believe all that God has revealed, all that He does now reveal, and we believe that He will yet reveal many great and important things pertaining to the Kingdom of God” (Article of Faith 9).