Here Oliver Cowdery omitted the an from before everlasting destruction as he copied the text from 𝓞 into 𝓟. All the printed editions have maintained this secondary reading. Elsewhere in the text, there are four occurrences of “an everlasting destruction”:
There are also two examples of everlasting destruction preceded by a different determiner:
But in two instances, there is no indefinite article (based on the earliest textual sources):
It therefore appears that everlasting destruction does not have to be preceded by a determiner in the Book of Mormon text. The critical text will in each case follow the earliest textual sources, thus “an everlasting destruction” here in Alma 27:4.
Summary: Restore in Alma 27:4 the indefinite article an before everlasting destruction, the reading of the original manuscript.