According to John Thompson, the structure and themes of Jacob's covenant speech show that he probably spoke in connection with a religious royal festival, to which the words of Isaiah which he quoted were especially well suited. . . .
Most biblical scholars divide Isaiah into three literary sections, composed of chapters 1-39, 40-55, and 56-66. . . . Mowinckel notes that there seems to be an association between the second division of Isaiah and the preexilic autumn festivals--namely the Feast of Tabernacles. . . . Engnell concluded that Isaiah 40-55 "is a prophetic collection of traditions" that may be called "liturgy, . . . not a cult liturgy but a prophetic imitation thereof."
The conclusions of these scholars are significant in light of the possible setting of Jacob's sermon, for if the second division of Isaiah, from which Jacob obtained his quotes, is a prophetic imitation of Sukkot liturgy (the Feast of Tabernacles ceremony), then it is possible that Nephi instructed Jacob to use Isaiah not only for the prophetic teachings and elevated language, but because Isaiah's words reflect the very festival in which they, the Nephites, were participating.
More importantly, Mowinckel, in his book entitled He That Cometh, declared that the Israelite festivals were a factor in forming the basis of a "future hope" for the Messiah, who is characterized as the "ideal" king. Further, he stated that the Messianic faith was "from the first, associated with the Jewish hope of a future restoration [of Israel]." . . . These two hopes--the Messiah and the restoration of Israel--are the very things that Jacob emphasizes in his sermon. For example, Jacob makes the following quote from Isaiah: "that ye may rejoice, and lift up your heads forever [that is, have hope], because of the blessing which the Lord God shall bestow upon your children. For I know that ye have searched much, many of you, to know of things to come" (2 Nephi 9:3-4). [John S. Thompson, "Isaiah 50-51, the Israelite Autumn Festivals, and the Covenant Speech of Jacob in 2 Nephi 6-10," in Isaiah in the Book of Mormon, pp. 136-138]