Jacob had been quoting Isaiah to remind us of the covenants the Lord has made with all Israel and that he has spoken by his servants, the prophets, from the beginning of time (Moses 5:58–59). Isaiah and Jacob show the hand of God in history (or, his story) and in the covenant blessings of repentance, forgiveness, gathering, restoration, and redemption.
Verses 1–3 constitute a doctrinal bridge to verse 4 and the verses following. Jacob moved from talking about the scattering and gathering of Israel to a discussion of physical death, and then to resurrection, because they are parallel. Death is the scattering of elements, and resurrection is the gathering or restoration of those elements. To Jacob and other Book of Mormon prophets, the doctrines of the gospel or plan of salvation are all interconnected—one seamless web.