Isaiah 53:7 (King James Bible) and as a sheep before her shearers is dumb so he openeth not his mouth
This is the second time Abinadi has quoted from this last part of Isaiah 53:7, but in this case the shearer is substituted for her shearers. This difference may indicate that in this passage Abinadi was not directly reading from a written text but instead was quoting from memory. Interestingly, the Greek Septuagint and the Latin Vulgate for Isaiah 53:7 use the singular form of shearer and without any pronominal modification—that is, both these ancient translations can be read as “and as a lamb before the one shearing is silent”. The Book of Mormon reading the shearer is therefore a possible reading and should be retained in Mosiah 15:7.
The use of the past-tense opened rather than the present-tense openeth (not only here in Mosiah 15:6 but also in Mosiah 14:7) is undoubtedly the original Book of Mormon reading for this Isaiah citation. See the discussion under Mosiah 14:7.
Summary: Retain in Mosiah 15:6 the shearer instead of her shearers; this reading is not supported by the Masoretic Hebrew text, but it is supported by the ancient Greek and Latin versions; Mosiah 15:6 also uses the past-tense opened, just like in Mosiah 14:7.