Cultural note: As Jacob shifts from text to commentary, he notes in passing that he has been reading the text from Isaiah. This is culturally significant to note in passing. The passages from Isaiah were read in public. Thus there is early in the Nephite society a model for the public use of written materials, and in particular written religious materials (though the difference between what constituted a religious document and what constituted a secular document was probably blurred it if existed at all).
Where there are times in the Book of Mormon where the scriptures appear to be cited from memory (Abinidi before Noah coming immediately to mind) it is also obvious that the texts were also read. In the case of Jacob, either he was using the actual brass plates, or a copy of those texts had been made. The very fact that we have the Isaiah passages in Nephi's record indicates that at least some copying of texts did occur. It is probable, however, that such copies other than Nephi's would have been made on perishable material rather than metal plates.
In the case of Jacob's sermon, however, the symbolic act of reading from the brass plates would add to the ceremony and import of the occasion, and I would therefore suggest that Jacob was probably reading directly from the brass plates, in full view of his audience.
Social Context: As has been noted, Nephi writes down Jacob's sermon without much preamble. There is no contextual information given, and anything we might surmise about the social context of the sermon must be extracted from the text. John S. Thompson examined this sermon for the thematic elements and textual structure, and suggests that based on textual analysis, the sermon fits the ancient Near Eastern covenant/treaty pattern:
"Though this pattern can vary in content and order, it typically follows a basic six-part form:
Thompson assigns the following sections of the speech to the formulaic pattern:
As a summary to his analysis of the covenant/treaty structure of the sermon, Thompson notes:
"Basing their arguments on covenant/treaty forms found in the biblical text, Gerhard von Rad and others have concluded that the Israelites periodically held a covenant-renewal ceremony during the Feast of the Tabernacles (Sukkot). Hence, the presence of this structure in Jacob's sermon may also suggest the possibility that he gave his covenant speech during this festival as well." (Thompson, p. 127).
Textual analysis: This verse is Jacob's transitional sentence between the cited passages and the commentary which will follow. Thus Jacob extracts from the Isaiah passages the single aspect of those passages that will become the focal point of his commentary - the covenants the Lord made with Israel. While this is a major aspect of the Isaiah passages, it is obviously a simplification. That is beyond Jacob's point.
For those who were able to understand in Isaiah the subtexts that Jacob might have been implying (at the suggestion of Nephi... perhaps relating to a mixed audience) the more subtle message had already been delivered. Jacob will now open his sermon to an extrapolation on Isaiah rather than a commentary as we would expect of the term today.
Verse 2 actually begins this extrapolation by enlarging the context of Isaiah. The Isaiah passages clearly mark promises of future salvation, but the call to repentance is current. In Jacob, the emphasis is encapsulated first into the future promises Isaiah states, and then is transformed into specific return/restoration promises. It is not easy to know precisely where Jacob is pulling his restoration theme. Perhaps he is keying on Isaiah 51:11:
(2 Nephi 8:11) 11 Therefore, the redeemed of the Lord shall return, and come with singing unto Zion; and everlasting joy and holiness shall be upon their heads; and they shall obtain gladness and joy; sorrow and mourning shall flee away.
If this is his text, he is playing loose with meanings, and keying on the return, rather than the fact that this is part of the complaint of Israel against the Lord, that the Lord was not hastening that day. Nevertheless, it is an image of return, and the Lord agrees implicitly that it is part of his covenant, as the following verses do not deny the request, but emphasize the lack of faith and patience on the part of Israel.
This theme of the return Jacob will use to move from Isaiah's text to the future history of Israel, and implicitly, the role of his audience in that future history.