Application to Israel and to Nephi's audience: Clearly for both Israel and Lehi's children their journeys in the wilderness become the quintessential "furnace of affliction." The exodus remained a tremendous part of the Israelite consciousness, and the personal struggles in the wilderness were even more present in the mind of Lehi's band. The Lord reminds them that the trials have their spiritual benefits, if they are willing to find them.
Textual analysis: The Book of Mormon removes a parenthetical phrase from the Isaiah text, which has "but not with silver" following the text "I have refined thee." Ludow notes:
"The King James Version phrase "but not with silver" is deleted from the Book of Mormon. It disrupts the flow of the verse so badly that many commentators have said that its "meaning is obscure," that it has "defeated all commentators up to the present," and that it was probably "altered by a scribe who took the meaning to be 'I have not sold thee for money.'" However, by omitting the phrase "but not with silver," the verse becomes dimple and clear. Perhaps this verse is an example of a "gloss," an addition made by a later scribe in order to clarify the verse as he understood it. If so, the gloss was assuredly written after 600 B.C. when the Brass Plates of Laban were taken from Jerusalem, because the phrase is not quoted in the Book of Mormon version of this verse." (Ludlow 1982, p. 404)
While the phrase "but not with silver" is indeed problematic, it is problematic only in the word "with." Note the following uses of the combination of "silver" and the refining process (here given as "tried"):
Ps. 12:6 The words of the LORD are pure words: as silver tried in a furnace of earth, purified seven times.
Ps. 66:10 For thou, O God, hast proved us: thou hast tried us, as silver is tried.
Zech. 13:9 And I will bring the third part through the fire, and will refine them as silver is refined, and will try them as gold is tried: they shall call on my name, and I will hear them: I will say, It is my people: and they shall say, The LORD is my God.
In each of these three cases there are important elements in common with the phrase in Isaiah - the refining process, and the use of silver as the exemplar of the refining process. In addition, both Psalms 66:10 and Zechariah 13:9 explicitly apply the example to the children of Israel. In that context, the appearance of "silver" in the Isaianic passage fits quite well with its theme of refinement through trial. The problem is that the "with" should better be read "as."
While I am unaware of the underlying Hebrew construction, this is the reading Avraham Gileadi gives:
"See, I am refining you, though not as silver; I am testing you in the crucible of affliction" (Gileadi, Avraham. The Book of Isaiah. Deseret Book Company. 1988, p. 191.