2 Nephi Chapter 8 is the text of Isaiah 51 and includes the first two verses of Isaiah 52. One of the interesting aspects of Isaiah in the Book of Mormon is that the 1830 verses which replicate the text of various Isaiah chapters do not always follow the chapter divisions as they appear in the Bible. Although our current edition created chapters between Isaiah 50 and 51 to follow the way they appear in the Bible, Jacob did not make a separation.
The quotation of Isaiah 50 addressed Israel in distress and emphasized that it was they who had left their God. The quotation of Isaiah 51 (and the first two verses of 52) are the admonition to look to their God for redemption.
In the midst of affliction, Jehovah admonishes Israel to look to their history. The image of the rock from whence they were hewn and the pit from which they were dug suggest that they are going back to their founding. Thus, Abraham is mentioned next. The bedrock on which they were built was Abraham, and Jehovah made covenants with Abraham that apply to his descendants.
Verse 3 is a reversal of the conditions described in the previous chapter. Through Jehovah’s redemption, their waste places will become as the Garden in Eden.
For Jacob’s audience, the emphasis is on the covenants with Jehovah that promise redemption. This would be a reinforcement of what had been the introduction of a new god to the previous inhabitants. While Abraham was not their literal ancestor, their adoption into Israel availed them of the blessings promised to Abraham and his descendants.