Verse 4 sets up a condition that leads to a very strong condemnation in verse 5. What in verse 4 is “most abominable above all sins save it be the shedding of innocent blood or denying the Holy Ghost?” I suggest that the most important aspect of Corianton’s sin was involved with abandoning his mission, which I hypothesize included personal apostasy rather than simply leaving his mission field.
In verse 3, Alma notes that “Thou didst do that which was most grievous unto me.” The very next thing Alma mentions is that Corianton forsook his ministry, which I read as falling into personal apostasy. In verse 5, Alma notes that something that Corianton did was “most abominable.” Immediately before that declaration is a repetition of the charge that Corianton had abandoned his ministry.
In-between these condemnations, Alma reprimands Corianton for following after the harlot Isabel. Certainly Alma did not approve of that action. Consorting with the harlot was a sin of sexual passion, but ultimately a forgivable one. Bruce W. Jorgensen, a professor of creative writing, suggests that the text stops short of declaring that Corianton actually committed more than the “lust of the eyes.” Even sexual transgression, however, does not merit the denunciation of being “most abominable above all sins save it be the shedding of innocent blood or denying the Holy Ghost.” What would be “most abominable,” however, would be Corianton’s denial of the gospel to embrace heresy. Such a sin would preclude forgiveness, not because it was impossible (as with the sin against the Holy Ghost, or murder), but because the apostate would have put himself in a position where he no longer had faith in repentance or in Christ’s power to save. One who will not repent is only slightly different from one who cannot.