The priests are ordained after the order of the Son. They take upon themselves a calling that is "without beginning or end." The Son is also without beginning or end. With these last two verses Alma tightly ties together the priesthood with the Son. In the Nephite understanding, this is the Atoning Savior. Thus once again Alma has tightly linked priesthood with the Atoning Messiah. Since Ammonihah does not believe in the Atoning Messiah, they cannot have the true priesthood.
Textual: This is the end of a chapter in the 1830 edition. It is not a chapter in the modern edition because there is no obvious break except the "Amen," and that word does not always end chapters, nor even sections. There is no indication of a break, and the theme of the following section continues to be this priesthood, thus the continuation in the modern edition.