Here both the 1830 edition and the printer’s manuscript are definitely firsthand copies of the original manuscript. 𝓟 has the pronoun it while the 1830 edition has he. We find in the very next verse an almost identical expression, and there both the 1830 edition and 𝓟 have the pronoun it:
There are no other occurrences in the text of “save he be”, but there are 47 other examples of “save it be”. This overall preference for “save it be” (as well as the specific occurrence of the phrase in the immediately following verse) could have inﬂuenced Oliver Cowdery to accidentally write “save it be” in 𝓟 rather than “save he be”, thus eliminating a unique reading, “save he be”, from the text. Also note that the it could have been prompted by the two nouns curse and land in the immediately preceding phrase (“because of the great curse of the land”).
In the Book of Mormon, the verb in save-clauses typically takes the subjunctive form when the subject is the indefinite it (mostly phrases of the form “save it be” and “save it were”). But when the subject is not it, the verb in the save-clause is almost always in the indicative. Even so, there are a few examples where the verb form takes the subjunctive, as in these two examples from the original text where the subject is the pronoun he:
In the first example, Joseph Smith emended the subjunctive know to the indicative knows in his editing for the 1837 edition (for discussion, see under that passage). In any event, these two examples show that there is internal evidence for the subjunctive usage “save he be”, the reading in the 1830 edition for Helaman 13:18.
Although “save it be” is very frequent in the Book of Mormon text, none of these occurrences are conjoined with a following predicate (except possibly here in 𝓟 for Helaman 13:18). And it is that predicate which argues that “save he be” should be the reading of the original text for this passage:
In other words, “save he … shall hide it up unto the Lord”. Quite clearly, “save it … shall hide it up unto the Lord” is unacceptable. It should be pointed out, however, that this conjunctive phraseology suggests two possible emendations for which the phrase “save it be” could be maintained:
There is evidence elsewhere in the text for the loss of the subject pronoun he (see the list of examples under Jacob 5:1–2). But there is no evidence for mix-ups between and and relative pronouns. So only the first of these two conjectural emendations has any independent support from errors in the transmission of the text.
Ultimately, the critical text will accept the reading of the 1830 edition in Helaman 13:18 as the original reading, mainly because it works perfectly well. The pronoun he is precisely what the following conjoined predicate requires (“save he … shall hide it up unto the Lord”). And the substitution of an original he with it (the reading in 𝓟) is quite probable given the dominance of the phrase “save it be” elsewhere in the text.
Summary: Accept in Helaman 13:18 the 1830 reading “save he be” as the probable reading of the original manuscript; Oliver Cowdery seems to have accidentally substituted it for he in 𝓟, probably because “save it be” is such a common expression in the Book of Mormon text.