"Critics have long adopted the cynical position that Joseph Smith simply copied the King James Version (KJV) Bible text for the relevant portions of Isaiah, Malachi, and the Sermon on the Mount. Even some Church members have presumed that the close match between the texts indicates that Joseph simply opened a Bible and copied those chapters when he came to material on the gold plates that he recognized as being from the Bible.
Did Joseph simply copy the KJV text?
There are several problems with this view....
We often find
differences in Book of Mormon Isaiah texts where modern texts disagree.[4] One verse (2 Nephi 12:16), is not only different but
adds a completely new phrase: "And upon all the ships of the sea." This non-King James addition agrees with the Greek (Septuagint) version of the Bible,
which had not been translated into English in Joseph Smith's day.[5]
It is also significant that the chapters of Isaiah actually quoted in the Book of Mormon (chapters 2-14 and 48-54) are those which modern scholars widely agree
correspond closely to the original Isaiah collection and therefore would have been the most likely to have existed in Lehi's day....
http://en.fairmormon.org/Book_of_Mor...s_from_the_KJV