These are probably the most common Bible verses used to attack the Book of Mormon. The following is important to consider when using those verses, as stated by Elder Holland of the Quorum of the Twelve Apostles:
“One of the arguments often used in any defense of a closed canon is the New Testament passage recorded in Revelation 22:18: ‘For I testify unto every man that heareth the words of … this book, If any man shall add unto these things, God shall add unto him the plagues that are written in this book.’ However, there is now overwhelming consensus among virtually all biblical scholars that this verse applies only to the book of Revelation, not the whole Bible. Those scholars of our day acknowledge a number of New Testament “books” that were almost certainly written after John’s revelation on the Isle of Patmos was received. Included in this category are at least the books of Jude, the three Epistles of John, and probably the entire Gospel of John itself. Perhaps there are even more than these.
But there is a simpler answer as to why that passage in the final book of the current New Testament cannot apply to the whole Bible. That is because the whole Bible as we know it—one collection of texts bound in a single volume—did not exist when that verse was written. For centuries after John produced his writing, the individual books of the New Testament were in circulation singly or perhaps in combinations with a few other texts but almost never as a complete collection. Of the entire corpus of 5,366 known Greek New Testament manuscripts, only 35 contain the whole New Testament as we now know it, and 34 of those were compiled after a.d. 1000.
The fact of the matter is that virtually every prophet of the Old and New Testament has added scripture to that received by his predecessors. If the Old Testament words of Moses were sufficient, as some could have mistakenly thought them to be, then why, for example, the subsequent prophecies of Isaiah or of Jeremiah, who follows him? To say nothing of Ezekiel and Daniel, of Joel, Amos, and all the rest. If one revelation to one prophet in one moment of time is sufficient for all time, what justifies these many others? What justifies them was made clear by Jehovah Himself when He said to Moses, ‘My works are without end, and … my words … never cease.’”
To read Elder Holland’s entire talk click here.
To see video of his talk click here.
We know that God continues to speak today!