By explaining that the Messiah’s coming must precede the resurrection, Alma confirms that Corianton’s problem with the resurrection is connected to his wavering faith in the Messiah. The Nehorite argument would be that one cannot know the future (Alma 30:15), and obviously, because the resurrection depends on the Messiah’s mission, the resurrection has not yet happened and, Corianton fears, will not happen.
Reference: The corruption/incorruption vocabulary echoes 1 Corinthians 15:42: “So also is the resurrection of the dead. It is sown in corruption; it is raised in incorruption.” “Corruption” refers to the mortal body’s inevitable decay after death. “Incorruption” refers to the resurrected body, which is no longer subject to death and decay.