There are numerous cases where a repeated indefinite article in a conjunctive noun phrase has been accidentally lost during the transmission of the text. (For a general discussion and listing of all the cases, see under conjunctive repetition in volume 3.) Here is an example where the form for the indefinite article is an rather than a. Its loss before eternal occurred in the 1837 edition, probably as a typo since its deletion was not marked in 𝓟 by Joseph Smith in his editing for the 1837 edition. Nor did Joseph ever remove instances of the repeated determiner in his editing. All instances of this error in the printed editions are accidental and are sporadic. In each case, we follow the earliest textual sources in deciding whether the determiner is repeated or not. The critical text will therefore restore the original repeated an here in Alma 34:10.
Summary: Restore the repeated indefinite article an in Alma 34:10 (“an infinite and an eternal sacri- fice”), which is consistent with numerous examples of repeated determiners found throughout the Book of Mormon.