Rhetorical: After asking if his people have been spiritually born, Alma immediately asks of they exercise "faith in the redemption of him who created you?" This is no accident, and follows both directly from the concept of being spiritually born as well as from the social issue that Alma is addressing. It is helpful to review one of the doctrinal statements that we have associated with Nehor so we can better understand what Alma is combating:
Alma 1:4
4 And he also testified unto the people that all mankind should be saved at the last day, and that they need not fear nor tremble, but that they might lift up their heads and rejoice; for the Lord had created all men, and had also redeemed all men; and, in the end, all men should have eternal life.
As was noted in the commentary on this verse, one of the essential aspects of this "doctrine" is the denial of the Atoning Messiah. The argument that "the Lord had created all men, and had also redeemed all men" is an attack against the necessity of the mission of the Savior. If God had already saved all of those he had created, there would be no need for a Savior. Thus one of the principle tenets of the Order of Nehor was the denial of the need for the Atoning Messiah.
It is for this very reason that Alma specifically asks his congregation if they "exercise faith in the redemption of him who created you?" Notice how directly this question combats the doctrine of the Nehors. Alma is very specifically asking his congregation to renew their covenants with Christ, and to remember the specific teachings about the Atoning Messiah that they have already accepted. Since this is the first sermon Alma delivers (at least of which we have record) after giving up the judgment seat to combat the religious contention, we should not be surprised if his text is pointed directly at the heart of the religious tension in the community. Indeed, this contention between the need for the Atoning Messiah that the Nephite prophets have preached, and the denial of that Atoning Messiah by some other organization (be it Lamanite, Noahite, or after the Order of the Nehors) is at the heart of most of the internal contentions in the Book of Mormon.