Verses 1 and 2 pick up the story that was interrupted in Alma 22:27. The first thing that the repetitive resumption does is to get the text back to the story that was interrupted. Thus, the idea that a proclamation was sent is repeated from Alma 22:27. The second aspect of the resumption is to tell why the proclamation was sent, which was not told before the inserted material on the geography of Lamanite and Nephite lands. The proclamation provided safety for the sons of Mosiah and for those with them in order to preach among the Lamanites. In Alma 22:26, Alma had told of the overking allowing the brothers to preach to those present, and this part of the story extends that permission to the whole of the territory over which the overking had control.
Verse 3 ends the part of the story that would have ended the previous chapter. In Mormon’s writings, it is not unusual for something to trigger him to end a chapter. When that happens, it also often happens that the story that would have ended the chapter isn’t over. That is the case here. Verse 3 summarizes the proclamation, and concludes that part of the story. The story will shift away from the overking and on to the next part of the missionary work, beginning in the next verse.