Here we have the first example of the subordinate conjunction that after the conjunction before. Such examples of archaic Early Modern English have been edited out of the text. In this particular instance, Joseph Smith marked the deletion in 𝓟. For a complete listing, see subordinate conjunctions in volume 3. See 1 Nephi 1:14 for because that and 1 Nephi 1:17 for after that.
Summary: Restore the archaic use of that after the subordinate conjunction before wherever it is supported by the earliest textual sources.