Reference/Translation: This verse may have either of two references. Nephi could easily have copied Isaiah 40:3–4: “The voice of him that crieth in the wilderness, Prepare ye the way of the Lord, make straight in the desert a highway for our God. Every valley shall be exalted, and every mountain and hill shall be made low: and the crooked shall be made straight, and the rough places plain.”
The second source, which it appears to follow more closely, is Mark 1:2–7:
As it is written in the prophets, Behold, I send my messenger before thy face, which shall prepare thy way before thee.
The voice of one crying in the wilderness, Prepare ye the way of the Lord, make his paths straight.
John did baptize in the wilderness, and preach the baptism of repentance for the remission of sins.
And there went out unto him all the land of Judaea, and they of Jerusalem, and were all baptized of him in the river of Jordan, confessing their sins.
And John was clothed with camel’s hair, and with a girdle of a skin about his loins; and he did eat locusts and wild honey;
And preached, saying, There cometh one mightier than I after me, the latchet of whose shoes I am not worthy to stoop down and unloose (see also Luke 3:16, John 1:27).
This passage gives us a glimpse into Joseph Smith’s translation process. The Book of Mormon passage would have communicated the meaning of the passage in either Isaiah or Mark. Joseph would have understood the meaning and made the connection to his own well-known King James Version. The relationship of text to translation is not a literal word-for-word translation of each word on the plates but a casting of the meaning of those words into phrasing that Joseph knew and understood. A number of these referents are from the New Testament, and it appears that Joseph was more conversant with the New Testament than the Old. In this case, Mark became the model for the English text, although Isaiah had to have been the model for Nephi’s text, since he would not have had access to Mark’s. This same phenomenon occurs several times throughout the Book of Mormon.