Redaction: When Jacob again picks up his stylus, he has a purpose in mind. He wishes to clarify a particular issue in the most permanent medium available to him: the metal plates. His approach to this task suggests that he is more comfortable in oral discourse than in writing. The current edition (1981) of Jacob 4 makes a stylistic shift between our verses 7 and 8.
All writers have an implied audience but typically do not address that audience directly. Jacob begins chapter 4 with a passage of explanation that is obviously, though not directly, addressed to his implied audience. As he writes, however, that audience becomes more explicit: Lehi’s descendants (vv. 2–3). Jacob soon (v. 8) shifts from exposition to direct address. It does happen that various plate-writers directly address their long-distant modern readers, but the nature of this address strongly suggests that it was given to a live audience and responded to a concern current in Jacob’s lifetime (vv. 16–17). It is another sermon, but not identified as such.
Narrative: Jacob, like Nephi (see commentary accompanying 1 Nephi 19:10 and 2 Nephi 25:1), begins writing on one topic, detours into a related topic, then finally returns to his original purpose. Jacob begins with a personal but formal declaration, introducing himself by name. But when he begins to explain his purpose in writing, he sidetracks himself with a parenthetical comment that, in English, leaves an incomplete sentence. When Jacob returns to his original intention (v. 8), he does not repeat a statement of purpose but creates a smooth transition (vv. 4–7). Jacob is moving from a description of his sermon into the text of the sermon. He is not obviously quoting the sermon until verse 10, but I see the sermon beginning with verse 8. It is also possible that the sermon began with our verse 4, and it takes Jacob from verse 4 to verse 10 to shift from description to oratory.
Jacob’s interpolation, a declaration-almost-apology that writing on the plates is so difficult that he writes little, turns into a reflection on the importance of the plates. He witnesses, as a prophet of God, that their message is essential.