Initially the original manuscript lacked the words “that ye shall”, but later on Oliver Cowdery inserted these words supralinearly in 𝓞 and with a slightly weaker ink flow. The printer’s manuscript also has the same words “that ye shall” inserted supralinearly, and there the correction seems to be virtually immediate (that is, there is no change in the level of ink flow in 𝓟). It is odd that both manuscripts have the insertion. One possible explanation is that only later Oliver decided to emend the text here as he was copying from 𝓞 into 𝓟; after adding “that ye shall” in 𝓟, he turned to 𝓞 and emended it as well (which would explain why the level of ink flow for the correction was slightly weaker in 𝓞 but the same in 𝓟). On the other hand, the correction seems so specific and the style so unlike current English, one is almost forced to think that Oliver simply made the same mistake twice: the original phraseology was difficult, and thus both times Oliver initially wrote the nonsensical but syntactically normal “whether they will come into their land”. Ultimately, it seems doubtful that Oliver himself would have made up the correcting language.
One thing we can demonstrate is that the modal verb shall in the correcting “that ye shall” is fully appropriate. First of all, earlier in the verse the text has ye shall: “and ye shall remain here”. Secondly, we get the following additional examples in the text where the main verb will (in the sense of ‘to wish, want, or desire’) is completed by a that-clause:
Of these 13 examples, 12 take a modal verb (5 with shall, 6 with should, and 1 with would ). Only Ether 15:34 omits the modal verb, and there the verb takes the subjunctive form be: “that I be translated”. In fact, the verb suffer in the following conjoined that-clause can also be viewed as a subjunctive form.
In the King James Bible, will is used 20 times in this same way (namely, as a main verb completed by a that-clause). This construction is found only in the New Testament. In 16 of these occurrences, the verb in the that-clause takes the subjunctive (that is, the infinitive form of a main verb), as in the following example that has the subjunctive be (like Ether 15:34):
In three cases the modal shall occurs:
Only once does should occur:
The Book of Mormon and King James examples suggest the following theoretically possible alternatives for Alma 27:15:
a different modal verb:
no modal verb at all:
The most reasonable possibility for Alma 27:15 seems to be the shall that is found in Oliver Cowdery’s supralinear correction in both manuscripts since the larger passage otherwise uses the present-tense modals: “I and my brethren will go forth into the land of Zarahemla and ye shall remain here until we return and we will try the hearts of our brethren”. The modal will, although theoretically possible, would sound odd if it were the original reading here in Alma 27:15 (“whether they will that ye will come into their land”).
Summary: Accept in Alma 27:15 the corrected reading in 𝓞 and 𝓟: “whether they will that ye shall come into their land”; the initial reading in both manuscripts (without “that ye shall”) is probably due to Oliver Cowdery’s difficulty in dealing with the unusualness in modern English of the construction “to will that ”.