Isaiah 51:19–20 (King James Bible) these two things are come unto thee who shall be sorry for thee desolation and destruction and the famine and the sword by whom shall I comfort thee thy sons have fainted they lie at the head of all the streets
John A. Tvedtnes (pages 87–88, “The Isaiah Variants in the Book of Mormon”, FARMS preliminary report, 1984) suggests that the sons in 2 Nephi 8:19 incorrectly replaced the things of the King James text under the influence of the several occurrences of the word sons in nearby verses:
Tvedtnes’s argument is that “these two” in verse 19 does not refer to two sons but to the conjunct “desolation and destruction” (as well as to the following parallel conjunct, “the famine and the sword”, which explains the cause of the desolation and destruction). Tvedtnes also argues that the thy before “desolation and destruction” in verse 19 of the Book of Mormon text is in error and should be removed. The resulting emended text, as recommended by Tvedtnes, would then agree with the King James text (and the underlying Hebrew text).
However, the Book of Mormon text for verse 20 has one additional phrase, “save these two”, which makes explicit the connection between the two sons in verse 19 and the two exceptional sons in verse 20 that have not fainted:
Verse 20 manifests one additional difficulty in the Isaiah text: if the sons have fainted, then how can they be as “a wild bull … full of the fury of the Lord”? The Book of Mormon text explicitly deals with this problem by adding the additional phrase “save these two”. In fact, it appears that verse 20 in the Book of Mormon variant connects Isaiah’s prophecy to John’s prophecy in Revelation 11 that describes the two prophets of God who will use incredible powers to hold back the armies of the nations that will surround the temple mount in Jerusalem prior to the second coming of Christ (see especially Revelation 11:5–6, which specifically refers to the powers of these two prophets). The additional phrase “save these two” in 2 Nephi 8:20 shows that the replacement in the preceding verse of the King James things with sons is fully intended and is not an error. Correspondingly, there is no reason to assume that the extra thy in verse 19 is an error.
Summary: Maintain the earliest text for 2 Nephi 8:19–20; the replacement of things with sons in the Book of Mormon text is intended since the next verse adds “save these two” after “thy sons have fainted”; the use of thy before “desolation and destruction” is perfectly acceptable since desolation and destruction (due to the famine and the sword) no longer need to be associated with the phrase “these two things ” (the King James text).