Jacob expands on the idea that he writes for future generations. It is not only for his own line, but also for “our beloved brethren.” That phrase often signifies future Lamanites, but it cannot be determined exactly how Jacob intended it. This record is being passed down through his lineage, as opposed to the regnal line of transmission of the large plates. The large plates would be assumed to be of value to all Nephites. A family record might not. Thus, it is possible that “our brethren” in this case refers to other Nephites. Whatever was in Jacob’s mind, we cannot know. We do know that in the modern day it became available to the Lamanites, and, therefore, that might be the prophetically intended meaning.
What Jacob hopes is that the writings will assist future generations in understanding that the Nephites knew of the atoning Messiah and the messages of all of the prophets from the plates of brass. This statement looks forward to what he is about to write, but does not look back to the previously recorded sermon. That was not the theme of the first chapter that Jacob wrote, which we have as chapters 1 through 3. That sermon admonished, but did not specifically teach, the hope of the Messiah’s glory. That is the message that Jacob is now about to write.