According to Cleon Skousen, the reader should notice that the last two verses of 2 Nephi chapter 8 comprise the opening portion of chapter 52 of Isaiah in our modern Bible. Jacob quoted them as though they logically belonged with Chapter 51 and treated them accordingly. Joseph Smith gave the meaning of these two verses in D&C 113:7-8:
Questions by Elias Higbee: What is meant by the command in Isaiah, 52d chapter, 1st verse, which saith: Put on thy strength, O Zion--and what people had Isaiah reference to?
He had reference to those whom God should call in the last days, who should hold the power of priesthood to bring again Zion, and the redemption of Israel; and to put on her strength is to put on the authority of the priesthood, which she, Zion, has a right to by lineage; also to return to that power which she had lost.
[W. Cleon Skousen, Treasures from the Book of Mormon, Vol. 1, p. 1247]
A Covenant Plan of Salvation
(2 Nephi--Enos)