Jacob concludes of his sermon with a plea for repentance. He asks the men to refrain from their iniquities, most specifically (due to its most recent explication) their forays into polygamy. His conclusion ties his plea to the doctrine of the second death. This is language that he has used earlier (2 Nephi 9:16,19,26), and which Nephi repeated (2 Nephi 28:23). We may assume that the this was probably a familiar teaching to the audience, and that it is simply touched on here with the expectation of understanding.