The earliest text here in Alma 17:38 is clearly defective since it first says that Ammon had killed six with the sling but then that he slew only the leader. One could, I suppose, argue that those that “had fallen by the sling” were only wounded, but this is directly contradicted by the preceding text:
We also have a later reference to what king Lamoni was told, as referred to by Ammon in the next chapter:
In his editing for the 1837 edition, Joseph Smith deduced from the difference between the number seven in Alma 18:16 and the number six in Alma 17:38 that Ammon had killed only one with his sword, so he inserted here in Alma 17:38 the phrase “with his sword” after “he slew none save it were their leader”. It is quite probable that the original text had some phrase like “with his sword” and that it was lost during the early transmission of the text. It is also possible that Mormon himself accidentally omitted the phrase in his own account. In any event, Joseph’s emendation here is quite reasonable and seems necessary. But three issues regarding the emendation need to be considered:
Was the determiner his or the?
Was the preposition with or by?
Did the phrase come after or before the save-clause?
We should note here that Joseph Smith’s phrase was not based on the original manuscript. All indications are that his editing for the 1837 edition was based on comparing the printer’s manuscript with the 1830 edition. Since the phrase is missing from 𝓟, we can assume that Joseph himself is responsible for choosing the specific phrase “with his sword” and placing it after the save-clause.
In the description of the battle between Ammon and the gang of robbers at the waters of Sebus, the text first refers to Ammon’s weapons as his: “with his sling” (verse 36), “with his sword” (verse 37), “with the edge of his sword” (verse 37). But later, in Alma 18, the determiner is the, not his: “and slew seven of their brethren with the sling and with the sword” (Alma 18:16). Since Alma 17:38 also reads “by the sling”, the odds are that the definite article the should be chosen for whatever phrase we supply in that verse in order to account for the death of the leader, the only one slain with the sword.
The second question is whether the preposition should be by or with. The preposition by occurs earlier in the verse (“fallen by the sling”), but for that prepositional phrase the verb is the intransitive fall (not the transitive slay). When referring to weapons, the preposition by, not with, occurs with the intransitive verb fall:
On the other hand, we get with as the preposition when the verb is the transitive “to fall upon someone”:
So the occurrence of “fallen by the sling” in Alma 17:38 is perfectly consistent with usage elsewhere in the text (that is, when the verb is the intransitive fall ).
On the other hand, when the verb is slay, the text favors with when referring to weapons, providing the verb slay is in the active, although by does occur twice under those conditions:
The text is equally divided between with and by when the verb slay is in the passive:
Since the verb slay in Alma 17:38 is in the active, the statistically more plausible preposition for the proposed emendation would be with. The choice of by on the grounds that it would parallel the preceding “fallen by the sword” is not particularly significant as an argument since there is really no possibility for the preposition with when the verb is the intransitive fall. Overall, with seems the more probable for the emendation here in Alma 17:38, which agrees in that respect with Joseph Smith’s own choice of with in his emendation, “with his sword”. Nonetheless, by remains a possibility.
The final question is where to place “with the sword”; there are three reasonable possibilities:
but with the sword he slew none save it were their leader
but he slew none with the sword save it were their leader
but he slew none save it were their leader with the sword
Usage elsewhere in the text argues that the second possibility is the most plausible. Normally in the text, instrumental adverbial phrases come after the verb, not before. For instance, in the preceding list where occurrences of the verb slay in the active have an instrumental prepositional phrase headed by either with or by, there is only one case where the prepositional phrase precedes the verb, namely, in Alma 50:26: “and they were determined by the sword to slay them” (instead of “and they were determined to slay them by the sword”). Normally, we expect “to slay X with the sword”, not “with the sword to slay X” (or “to slay with the sword X”):
Thus here in Alma 17:38, “he slew none with the sword” is more plausible than “with the sword he slew none” (or, even worse, “he with the sword slew none” or “he slew with the sword none”).
As far as placing “with the sword” after the save-clause, usage elsewhere in the text shows quite clearly that prepositional phrases acting adverbially are kept close to their verbs and not placed after the save-clause:
In accord with the consistency of these patterns, here in Alma 17:38 the critical text will place the phrase “with the sword” after “he slew none” but before the save-clause:
Summary: The text in Alma 17:38 requires some kind of emendation like Joseph Smith’s 1837 insertion of “with his sword”; based on usage elsewhere in the text, the critical text will insert “with the sword” (rather than “with his sword”) and will place it right before the save-clause, giving “but he slew none with the sword save it were their leader”.