Without attribution, the Savior quotes Isaiah’s prophecy that the Jews will accept Jesus; then “shall their watchmen lift up their voice, and with the voice together shall they sing.”
This method of using the scriptures reverses the typical method of exegesis, in which the teacher quotes the scripture and then explains it. The Savior has explained what would happen in the future, then punctuated the message with a scriptural confirmation. He is not explaining the scriptures but using them as final evidence of his explanation.
Reference: The quotation is from Isaiah 52:8: “Thy watchmen shall lift up the voice; with the voice together shall they sing: for they shall see eye to eye, when the Lord shall bring again Zion.”
Jesus had quoted Isaiah 52:8–10 on the first day (3 Ne. 16:18–20). During this particular discourse, he will quote most of Isaiah 52, but the verses are not in order. This fluid movement backward and forward through the text confirms that the Savior assumes that the people are familiar with it, requiring no citations, or perhaps that they remember it from the previous day. He expected his listeners to identify these quotations as they appeared in his discourse, understanding their combined contexts.