Literary: Nephi is resetting Isaiah 29:11. Because of the importance of the thematic transition, verse 10 is also noted here:
Isa. 29:10
10 For the LORD hath poured out upon you the spirit of deep sleep, and hath closed your eyes: the prophets and your rulers, the seers hath he covered.
11 And the vision of all is become unto you as the words of a book that is sealed, which men deliver to one that is learned, saying, Read this, I pray thee: and he saith, I cannot; for it is sealed:
Of course in Nephi’s recasting , he has reset the “voice from the dust” from Isaiah’s demeaned people to the voice of those who have died (he does this first in 2 Nephi 26:15) In this verse, the “slumbering” has a dual function. In the previous verse “sleep” refers to those whose eyes were closed to the gospel. In this verse “sleep” refers to the destroyed Nephite nation whose record is being discussed.
Not only does Nephi use a sleep as a literary turning point to shift meaning, but he also creates an interesting tension between the world and the words of the slumbering Nephites. The “slumbering” will bring salvation to those who are as though asleep. by using the same imagery for both ends of the continuum, Nephi inextricably ties them together in intent and purpose. The slumbering of the Nephites is for the sleep of the rulers and wise of the word. The effect will be the awakening of the world to the gospel (and thereby the eventual redemption of the Nephites who sleep).
It is also interesting to note that in the recasting of Isaiah Nephi makes a split here in the base text. Nephi uses the theme of sleeping to move his vision along, but the explanation of the book now comes to the fore. The important part of the verse for Nephi’s current examination is the nature of the sealed book itself. The next verses are descriptive of the “sealed” book and are not directly based upon Isaiah. Nephi will return to Isaiah when he is ready to return to the delivery of the sealed book to the learned man.