Jacob begins the second day of his sermon by referring to the topic he began at the end of the previous day’s sermon. He is speaking of the righteous branch of Israel. Lehi had taught some version of the allegory of the olive tree, and Jacob will provide the full allegory in his own book. At this point, he simply refers to the branch with the assumption that his listeners will understand what he means. This suggests that the allegory of the olive tree, which Lehi taught and Nephi reinforced, was part of the common understanding by this time. Most of the lessons of the righteous branch had dealt with the Nephites being gathered back to Israel. Jacob will shift that emphasis.
Jacob spoke the day before to a people he believed required repentance. He will now combine that problem of disobedience to the law with the teaching he gave concerning the coming Messiah. The simple presence of the Messiah will not be sufficient to turn a people to righteousness.
Jacob specifically points these lessons at his audience, reminding them that they have received promises according to the flesh. There are promises of safety upon righteousness, but destruction, if they are not righteous. Jacob repeats the prophetic promise that many will perish, but some will survive. Although that is in the future, he undoubtedly hoped to awaken in his audience the need for repentance to forestall the prophesied destruction.