Here scribe 3 of 𝓞 originally wrote thus is, but later scribe 2 of 𝓞 corrected the grammar of the text, from “thus is the words” to “thus are the words”. Later, in his copying from 𝓞 to 𝓟, Oliver Cowdery misread scribe 3’s thus as these, with the result that the editions have consistently read “these are”.
Let us consider the grammatical change first. As already noted, nonstandard subject-verb agreement occurs in the original text. A similar example (but left unedited in the first two editions) is found near the end of 1 Nephi:
Here the 1840 edition changed the singular is to are (just as scribe 2 of 𝓞 emended scribe 3’s is to are in 1 Nephi 8:34). The 1852 LDS edition solved the problem in subject-verb agreement by changing the logical subject covenants to the singular covenant. The critical text will retain the original “thus is” in both 1 Nephi 8:34 and 1 Nephi 22:6. See further discussion under subjectverb agreement in volume 3.
Now let us turn to the replacement of thus with these. This kind of mistake in transmission is found elsewhere in the text, as in the following example where the 1830 compositor misread thus as these:
There are quite a few examples where thus is used in this way, as in the example listed above of 1 Nephi 22:6 (“for thus is the covenants of the Lord with our fathers”). For further discussion of the use of thus in summarizing, see Helaman 16:8–11.
The word thus in 1 Nephi 8:34 refers to Lehi’s actual words in the previous verse, which are in the first person:
The words in the second half of verse 34 (after the summarizing thus-clause) are in the third person and represent an explanation by Nephi (as evidenced by the use of the conjunction for):
Even with the reading these, the reference is still the preceding quote in verse 33. Therefore, there is no need for the colon after father in verse 34; a comma would be more appropriate.
Summary: Restore the nonstandard “thus is the words of my father” in 1 Nephi 8:34; the thus refers the reader back to the words of Lehi directly quoted in the previous verse; as a result, a comma, not a colon, should precede the following for-clause (“for as many as heeded them had fallen away”).