Malachi 4:3 (King James Bible) for they shall be ashes under the soles of your feet in the day that I shall do this
Here we have two more minor variants in the text, including one more by the typesetter for the 1841 British edition, namely, the replacement of the determiner the with that (thus changing “in the day that I shall do this” to “in that day that I shall do this”. The that was apparently prompted by the subordinate conjunction that in the following clause (“that I shall do this”). In any event, the correct the was restored in the subsequent LDS edition (1849). For a more complicated case of “in the day” versus “in that day”, see under Helaman 14:20.
The second minor variant in this passage involves scribe 2 of 𝓟, who initially wrote “they shall be as ashes” in 𝓟 but virtually immediately corrected the text by crossing out the as (there is no apparent change in the level of ink flow for the crossout). Scribe 2 was probably influenced by the phraseology “they shall be as …” as well as by the word-initial as of the following word, ashes. In the Book of Mormon text, the as is usually lacking in the phrase “they shall be (as) ” (as in 3 Nephi 20:28: “and they shall be a scourge unto the people of this land”), but there are a few examples of “they shall be as ”:
The use of the as in the two examples from 2 Nephi 26 follows the language of Isaiah 47:14 (“behold they shall be as stubble”). Although the example here in 3 Nephi 16:15 is related to Matthew 5:13, there is no as in the biblical version (“but if the salt have lost his savor”), nor when it is quoted in 3 Nephi 12:13 (“but if the salt shall lose its savor”). The critical text will in each of these cases follow the earliest textual sources, thus no as here in 3 Nephi 25:3.
Summary: Maintain in 3 Nephi 25:3 the reading of the earliest textual sources without the as (“they shall be ashes”), which is also the corresponding reading in Malachi; also maintain the definite article in the phrase “in the day”.