[𝓢① that >+ 𝓢② & 0|& 1|and ABCDEFGHIJKLMNOPQRST] there cannot any unclean thing enter into the kingdom of God
Here we have two changes involving the subordinate conjunction that. When copying from 𝓞 to 𝓟, Oliver Cowdery omitted the first that, probably accidentally. There are numerous examples throughout the Book of Mormon textual history of the accidental deletion of the subordinate conjunction that, especially after the verb say. (See the examples listed under that in volume 3.) Oliver Cowdery also changed the second that to and; he made this change in the original manuscript by crossing out the that with heavier ink flow and supralinearly inserting an ampersand. The ampersand was copied into 𝓟. Another possibility would have been to simply insert an and before the that (that is, without deleting the that). In fact, it is quite possible that scribe 2 of 𝓞 left out an and before the second that. We already have seen examples of scribe 2 leaving out and ’s (see the list under 1 Nephi 12:11). The Book of Mormon text has numerous examples of that- clauses conjoined by means of the conjunction and, including the following two examples in this same chapter:
See the discussion under 1 Nephi 15:24.
However, there appears to be at least one other example in the earliest text of two conjoined that-clauses without a connector. And in this case, the textual tendency has been to change the second that to and, just like in 1 Nephi 15:34:
The original manuscript for 3 Nephi 3:26 undoubtedly had both that’s but no and since in 3 Nephi both 𝓟 and the 1830 edition are firsthand copies of 𝓞 and for this passage both read identically. The replacement of the repeated that with and was made in the 1849 LDS edition, perhaps by Orson Pratt in his minor editing for that edition. Since we do have a couple cases (in 1 Nephi 15:34 and 3 Nephi 3:26) where the original manuscript apparently read without such an and, we should accept such readings and restore them to the critical text, despite their infrequency.
There is a third example of a sequence of two that-clauses without a connecting and, but here the second that-clause is a resultive clause and thus differs from the first that-clause:
In this instance, the second that means ‘so that’. Despite this difference in meaning, this second that was also replaced by and (in this case, in the 1840 edition and also in the 1920 LDS edition), showing that a sequence of that-clauses without a connector was considered awkward, even if intended. (See the discussion under 1 Nephi 13:15.)
Summary: Restore the reading of the earliest text in 1 Nephi 15:34 by restoring both that ’s, but without adding any connecting and; a similar example is found in the earliest text for 3 Nephi 3:26; the tendency has been to change the second that to an and in order to alleviate the awkwardness of the original phraseology.