Isaiah 49:7 (King James Bible) to him whom man despiseth to him whom the nation abhorreth to a servant of rulers kings shall see and arise
The indefinite article a before servant is not in any of the manuscripts or editions of the Book of Mormon, yet the current reading seems quite awkward and suggests that the use of the article in the King James text is wholly appropriate (and perhaps even necessary for English readers). I doubt that the lack of the a in the Book of Mormon text should be explained as a Hebraism. There is no indefinite article at all in Hebrew, yet the indefinite article a/an is virtually always maintained in the Book of Mormon quotations of the King James Bible. For instance, in the King James version of Isaiah 48–49, there are 13 other occurrences of the indefinite article a and 3 of the variant an, yet all of these other occurrences of a/an were correctly transmitted into the corresponding Book of Mormon text (1 Nephi 20–21). In only a handful of cases do we have instances where a King James indefinite article is missing in the Book of Mormon text. See 2 Nephi 7:11 and Alma 42:2 for two examples where the a of King James phraseology was accidentally omitted because of difficulty Oliver Cowdery had in hearing the a.
Here in 1 Nephi 21:7 it appears that the a was accidentally dropped from the text as Oliver Cowdery took down Joseph Smith’s dictation. In fact, Oliver initially wrote for instead of the to (the text reads “to a servant of rulers” in the King James Bible). Oliver later corrected the for to to (but with weaker ink flow). Perhaps because Oliver initially misheard or misinterpreted the to as for, he may have also omitted the indefinite article at the same time.
Summary: Add the indefinite article a in 1 Nephi 21:7 so that the text reads “to a servant of rulers” (the reading of the King James Bible); the current text without the a (“to servant of rulers”) is very awkward and suggests an early error in the transmission of the text; Oliver Cowdery probably dropped the a here when he initially wrote down the wrong preposition ( for instead of to), and this error may have interfered with his writing down the a.