In the printer’s manuscript, Oliver Cowdery originally wrote “things which is hoped for”, which he later corrected (with somewhat heavier ink flow) to the fully plural “things which are hoped for”. Evidence suggests that the plural are was the reading in the original manuscript; Oliver probably wrote the singular is because of the preceding is in “faith is things”. 𝓞 is not extant here, but this change from is to are in 𝓟 does not appear to be the result of editing on Oliver’s part since he otherwise wrote down numerous instances of subject-verb disagreement without emendation in this part of the text, as in these examples in relative clauses:
Thus here in Ether 12:6 it is much more likely that Oliver made the change in 𝓟 from is to are because 𝓞 itself read are. (For a complete list of cases of subject-verb disagreement in the text, see under subject-verb agreement in volume 3; also see the discussion under 1 Nephi 4:4.)
Here Ether 12:6 paraphrases the King James language in Hebrews 11:1:
Based on the parallelism, the singular is after faith in Ether 12:6 is probably intended, even though in the Book of Mormon version the following plural things is awkward given the preceding is (the singular substance in the King James text avoids this problem in agreement). A similar is followed by are is found in another Book of Mormon passage that refers to faith:
In his editing for the 1837 edition, Joseph Smith grammatically emended the is in that passage to are, giving “ye hope for things which are not seen which are true”.
Summary: Maintain in Ether 12:6 the corrected reading in 𝓟: “faith is things which are hoped for and not seen”; given Oliver Cowdery’s scribal practice, 𝓞 probably read “which are hoped for” rather than “which is hoped for”.