Isaiah 48:8 (King James Bible) for I knew that thou wouldest deal very treacherously and wast called a transgressor from the womb
When Oliver Cowdery copied from 𝓞 to 𝓟, he accidentally replaced the definite article the with the pronominal possessive thy, probably because this whole passage in Isaiah continually uses the second person pronominal forms (such as three preceding occurrences of thou and one of thine in this verse). David Calabro points out (personal communication) that if this reading with thy were to make any sense, we would need to emend the whole phrase to read “from thy mother’s womb”.
The thy in 𝓟 was later crossed out with heavy dark ink, and the correct the was supralinearly inserted. Multispectral imaging of the ink agrees with the nearby corrections Joseph Smith made on the manuscript when he edited the text for the 1837 edition. In addition, the handwriting seems to be Joseph’s rather than the 1830 typesetter’s (that is, John Gilbert’s). The 1830 edition has the correct the, which implies that the 1830 typesetter may have once more checked his King James Bible to make the text conform to the Isaiah text. This interpretation would mean that in this instance Joseph Smith corrected 𝓟 to make it agree with the 1830 edition.
One other possibility is that the correction in the printer’s manuscript is not Joseph’s, but actually the 1830 typesetter’s. We know this is a possibility since later on, in 2 Nephi 20:10, the 1830 typesetter supralinearly inserted in 𝓟 the words did excel, which Oliver Cowdery had not copied into 𝓟. We also know that in the extensive quotation from Isaiah in 2 Nephi 12–24, the 1830 typesetter systematically used his King James Bible to determine the punctuation and the spelling for these Isaiah chapters. It would not therefore be surprising if he used his Bible to do the same in 1 Nephi 20:8—and even to mark the correct reading in the printer’s manuscript. But the handwriting of did excel of 2 Nephi 20:10 looks much different than the correcting the found in 𝓟 for 1 Nephi 20:8.
Summary: Despite the shifting in 𝓟 for 1 Nephi 20:8 (from the to thy and then back to the in the phrase “from the womb”), the critical text will maintain the the of the original manuscript, which also agrees with the reading of the King James Bible.