Nephi did not make the small plates until the Lord told him to do so, some thirty years after Lehi’s colony had left Jerusalem (see 2 Nephi 5:28–31). Nephi did not understand why he was to make a second set of records, but he had faith that it was “for a wise purpose in him [the Lord], which purpose I know not” (1 Nephi 9:5). Nearly a thousand years later, the prophet Mormon echoed words similar to Nephi’s when he testified that along with his abridgment of the large plates of Nephi he was including the small plates of Nephi “for a wise purpose” (Words of Mormon 1:7).
Joseph Smith started the translation of the Book of Mormon with Mormon’s abridgment of the large plates of Nephi. He had completed 116 manuscript pages when Martin Harris pleaded with Joseph to let him take the manuscript and show it to family members. Joseph pleaded with the Lord and eventually Martin’s request was granted. The manuscript fell into the hands of wicked men (see D&C 10:8) and became known as the “Lost Manuscript.”
The loss of the manuscript makes it apparent why the Lord commanded Nephi and Mormon to do what they did. Joseph Smith was told not to retranslate the portion he had already completed, but to translate the small plates of Nephi (see vv. 30, 38–45).
“The Lord knoweth all things from the beginning; wherefore, he prepareth a way to accomplish all his works among the children of men” (1 Nephi 9:6). The Lord inspired Nephi and Mormon to do the necessary things that would allow his work to be accomplished by Joseph Smith, even though they were all separated from each other by hundreds of years.