The original text sometimes permitted the repetition of therefore. Earlier in this chapter, in verse 6, Joseph Smith removed the repeated therefore in his editing for the 1837 edition. There he crossed out the second therefore in 𝓟. But here in verse 9, he did not cross out the repeated therefore in 𝓟. Nonetheless, it was omitted in the 1837 edition (it was probably crossed out in the copy of the 1830 edition that served as the copytext for the 1837 edition). The 1908 RLDS edition restored the repeated therefore here in verse 9 since it was not crossed out in 𝓟, but that edition did not restore it in verse 6 since it was crossed out there in 𝓟. To be sure, the repeated therefore seems less irritating here in verse 9 because of the long intervening text between the two therefore ’s, unlike the earlier case in verse 6 where the two therefore ’s are quite close to each other (“therefore as they were cut off from the tree of life / therefore they should be cut off from the face of the earth”). As explained under 2 Nephi 5:21, the critical text will restore such instances of the repeated therefore, despite their redundancy.
Summary: Restore the repeated therefore in Alma 42:9 as well as earlier in Alma 42:6; the original text allowed this kind of redundancy.