Isaiah 48:4 (King James Bible) because I knew that thou art obstinate and thy neck is an iron sinew
The original manuscript shows a difference in tense for this passage—the present-tense art followed by the past-tense was. In the Hebrew original, the linking be verb is unstated. The King
James Bible provides two italicized present-tense forms, art and is. In the Book of Mormon textual history, there have been two attempts to resolve the disagreement. In the 1852 LDS edition, the art was changed to wert (thus making both verbs in the past tense). But for the 1920 LDS edition, the present-tense art was restored and the was was changed to is, making the tenses agree with the King James Bible.
It is possible to argue that the original text actually read is and that the is was accidentally changed to was because of the preceding past-tense knew (as well as the preceding past-tense clause “and I did it”). Nonetheless, we should note that there is the intervening present-tense art.
Generally speaking, the critical text will retain the reading of the earliest textual sources for the biblical quotations in the Book of Mormon, even when they disagree with the King James Bible—unless there is substantial reason to think that there is some error in the transmission of the quotation. Our basic procedure is that if the earliest Book of Mormon reading works, we will retain it. These principles, when applied here in 1 Nephi 20:4, require that we retain the mixture of tenses, “art obstinate” but “was an iron sinew”. For another example of such a mixture in tense, see 1 Nephi 20:13.
Summary: In general, the critical text will maintain the reading of the earliest textual sources; here in 1 Nephi 20:4, the earliest reading (in 𝓞, 𝓟, and the 1830 edition) has a present-tense art and a pasttense was; in the original Hebrew, there is in each case an implied be verb unspecified for tense; the King James Bible translates both cases in the present tense and puts the words art and is in italics.