The original language in verse 9 (which has been retained in the LDS text) is undoubtedly intended since it is repeated in verse 11 (with variation only in the placement of the phrase of thyself ):
The first occurrence of the if-clause (in verse 9) is fully extant in 𝓞; the second (in verse 11) is not except for the very end of the clause:
The variation in the placement of the phrase of thyself is found in 𝓞 itself, which means that this slight syntactic difference in the angel’s language should be retained in verses 9 and 11.
The use of uncompleted positive if-clauses with a negative meaning is characteristic of strong imperative and declarative statements in Hebrew. Similar Hebrew-like uses of uncompleted conditional clauses can be found elsewhere in the Book of Mormon text. See, for instance, the examples discussed under 1 Nephi 19:20–21 and Alma 30:39. For a general discussion of uncompleted conditional clauses, see under hebraisms in volume 3.
The same basic type of if-clause is also found in the earlier account of Alma’s conversion; this account also quotes the words of the angel to Alma:
In this instance, the if-clause uses a different verb (“cast off ”) while the phrase of thyself precedes the verb (as in Alma 36:9). But a more significant difference between the Mosiah 27 example and the two examples here in Alma 36 is the occurrence of even before the if in Mosiah 27:16 (“and this even if thou wilt of thyself be cast off”). In theory, the word even can be attached either to the preceding this (“and this even / if thou wilt of thyself be cast off”) or to the following if (“and this / even if thou wilt of thyself be cast off”). Usage elsewhere in the text argues for the latter possibility since there are no other occurrences of this even, but even if is fairly frequent:
Moreover, there are instances of and this in the text, as in “and this because of your iniquities” (1 Nephi 3:29). The most reasonable syntactic interpretation for Mosiah 27:16 is “and this / even if thou wilt of thyself be cast off ”.
David Calabro has suggested (personal communication) that the two instances of the if-clause in Alma 36:9, 11 should be interpreted as meaning ‘even if ’. The use of even in Mosiah 27:16 implies a negation, which may explain why the if-clause there has not undergone any grammatical emendation. On the other hand, the two instances in Alma 36 do not have the even, and both of these have undergone the same grammatical emendation in the 1852 LDS edition and in the 1953 RLDS edition—namely, the insertion of the negative not after the modal verb wilt: “if thou wilt not be destroyed”. But in the second printing of the 1852 edition, both cases of this intrusive not were removed (the corrections were made in the stereotyped plates), with the result that no not shows up for this clause in subsequent LDS editions.
Another possible grammatical emendation for the two unusual if-clauses in Alma 36, where the even is lacking, would be to replace the subordinate conjunction if with unless (the corresponding negative conjunction):
In any event, the consistency of the usage in Alma 36:9, 11 (an if-clause where negation is implied) argues that this construction, without any supplied not or other negative element, is fully intended as an instance of the uncompleted Hebraistic conditional clause. The critical text will retain these two instances of the negative if-clause in Alma 36, despite the difficulty they cause for English readers. The standard LDS and RLDS editions have generally resisted supplying an overt negative marker for this particular if-clause.
Summary: Accept in Alma 36:9, 11 the use of two uncompleted if-clauses with their implied negative; the related warning from the angel in Mosiah 27:16 contains the implicitly negative even, “and this / even if thou wilt of thyself be cast off ”; also accept the syntactic variation regarding the placement of the phrase of thyself in these if-clauses since this difference in word order is supported by the original manuscript in the case of the two Alma 36 examples.