Isaiah 53:6 (King James Bible) and the LORD hath laid on him the iniquity of us all
In the Mosiah 14 quotation of Isaiah 53, the Book of Mormon text pluralizes several references to evildoing that involve the words iniquity, transgression, and sin. There are three instances where the plural already occurs in the corresponding King James text (and in the Masoretic Hebrew):
On the other hand, there are three places where Isaiah 53 reads in the singular in the King James Bible (and the Masoretic Hebrew) but in the plural in Mosiah 14. Besides iniquities in Mosiah 14:6, we have one case of sins, plus one more of transgressions:
Interestingly, for all six of these cases, the Greek Septuagint also uses words in the plural to refer to evildoing (translated as either sins or lawless acts). The consistency in the use of the plural for Abinadi’s citation of Isaiah 53 definitely implies that this plural usage is intentional and was originally in the Book of Mormon text. (Also see under 2 Nephi 24:21 and Mosiah 13:13 for additional examples where the Book of Mormon text favors the plural iniquities instead of the singular iniquity of the King James Bible.) The critical text will therefore maintain these three additional cases of plural usage in Mosiah 14.
Summary: Retain in Mosiah 14 all the plural instances that refer to evildoing (namely, the words iniquities, transgressions, and sins), including the three cases (in verses 6, 8, and 12) where the King James Bible and the Masoretic Hebrew text read in the singular; for these three cases, the Greek Septuagint reads in the plural, just as do all the (extant) textual sources for Mosiah 14.