Malachi 3:16 (King James Bible) then they that feared the LORD spake often one to another and the LORD hearkened and heard it and a book of remembrance was written before him …
The Book of Mormon text lacks the pronoun it after heard. This pronoun is in italics in the King James Bible and is therefore subject to alteration in the Book of Mormon text. The earliest textual sources indicate that the original manuscript did not have the it. And the current text, both LDS and RLDS, continues to follow this reading.
Elsewhere in this quotation from Malachi, there are longer italicized King James phrases that have also been excluded from the Book of Mormon text:
In these cases, as with the it in Malachi 3:16, the unnecessary italicized phrase has been omitted in the Book of Mormon text. For examples involving a single word, see the discussion regarding you under 3 Nephi 12:11 and do under 3 Nephi 13:7.
Summary: In 3 Nephi 24:16, a direct object pronoun it after heard is not supported by any of the Book of Mormon textual sources; it occurs in italics in the King James version of Malachi 3:16 and is therefore subject to deletion; the critical text will therefore maintain the invariant Book of Mormon reading without the it.