According to Jeff Lindsay, the idea of a simple-minded copying by Joseph Smith of Bible passages into the Book of Mormon has to be rejected, though it is clear that the King James Bible was used in many cases to facilitate translation. In actuality, scholars have found that Book of Mormon passages apparently from the King James Version of the Bible contain variants corroborated in other biblical manuscript texts. Franklin Harris writes:
In Isaiah 14:4 (2 Nephi 24:4) the Book of Mormon adds "And it shall come to pass in that day," which is without support in the Hebrew. But of striking interest is a similar reading in Codex Alexandrinus (now in the British Museum), "And thou shall say in that day." The latter is not found in (Codex Vaticanus. . . ." (Franklin S. Harris, Jr., The Book of Mormon: Messages and Evidences, pp. 50-52)
[Quoted by Jeff Lindsay, "Did Joseph Smith Plagiarize from the King James Bible?," Book of Mormon Commentary, [www.jefflindsay.com]]