The parallel sections continue. These verses parallel verses 16 and 17 in their intent. In the previous verses, as well as in these, the subject is each individual being presented to God in the final judgment, but without having experienced the mighty change of heart that leads to exercising faith.
Alma declares that those who actively reject the covenants of God are effectively yielding themselves to become subjects of the Devil. The reason for this dramatic statement is that scriptures typically paint pictures in only black and white. Thus, there are two churches, the church of God or the church of the Devil (see 1 Nephi 14:10). Therefore, if one does not exercise faith in God’s covenants, they must therefore belong to the opposite possibility. Of course, there is an earth-life full of the possibility of repentance before such a dramatic choice is applicable, and degrees of glory after that. Those nuances are not important to this sermon.
Alma emphasizes that there is only one way to salvation and reiterates that it is “through the blood of him of whom it has been spoken by our fathers.” Once again, the emphasis is on the coming Messiah. This continues to suggest that this congregation, at least, has members who have rejected the belief in the coming Messiah.