Isaiah 14:13 (King James Bible) for thou hast said in thine heart
In Early Modern English, h-initial words were often pronounced as vowel-initial (in other words, the h was silent). As a consequence, an, mine and thine occurred with such words (instead of a, my, and thy), providing the h was silent. We have already noted the use of an in the King James text for Isaiah 2–14, while in the corresponding Book of Mormon quotation, a replaces an in such cases (see the discussion under 2 Nephi 13:7).
Yet when we consider my and thy for Isaiah 2–14, we find that in nearly all cases of h-initial words, the Isaiah of the King James Bible has my and thy rather than mine and thine:
For all of these examples, the corresponding Book of Mormon usage is identical to the King James usage (that is, my and thy before these h-initial words). The only exception in Isaiah 2–14 of the King James Bible is thine heart in Isaiah 14:13, which corresponds with thy heart in 2 Nephi 24:13. Thus the Book of Mormon’s thy heart is more consistent with respect to other h-initial words in this long Isaiah passage. (For further discussion of this issue, see under possessive pronouns in volume 3.)
Summary: Maintain the more consistent use of thy before the h-initial heart in 2 Nephi 24:13.