While the intent of the prophecy is contained in Nephi’s revelation (presumably part of his vision of the tree of life), this wording is not. However, verses 14–17 appear to be a quotation because they are spoken in prophetic first person, with the prophet uttering Yahweh’s words. Apparently, since Jacob does not identify the prophet, his listeners were familiar with it, even though it is unknown to modern readers. The wording and the theme are so closely related to Nephi’s vision that I conjecture it is a quotation from the longer version preserved on the large plates.
Culture: The emphasis on the “king” is a direct allusion to Isaiah, but it is also a reminder of Nephi’s reluctance to become a king: “And it came to pass that they would that I should be their king. But I, Nephi, was desirous that they should have no king; nevertheless, I did for them according to that which was in my power” (2 Ne. 5:18). Despite Nephi’s stated preference that the people have no king, Jacob has reminded his listeners that they look to Nephi as a king (2 Ne. 6:2). Nephi’s obvious functioning as king is confirmed in Jacob 1:9 when Nephi’s successor becomes a king. Clearly, Nephi is not the king Jacob is referring to in this verse.
The sense that a king represents a threat against the Lord still fits best into the reconstructed scenario of a people surrounded by other nations—in this case, nations with kings and ideologies hostile to the Nephites who represent Zion.