Jesus’s previous message had dealt with events of the end-times. His instructions now deal with record-keeping. Jesus knows that the Nephites are record-keepers and have Isaiah’s record. He emphasizes that he just quoted a major section of Isaiah as a transition to instruct his listeners to study Isaiah “diligently,” a repetition of his earlier command: “Ye remember that I spake unto you, and said that when the words of Isaiah should be fulfilled—behold they are written, ye have them before you, therefore search them” (3 Ne. 20:11).
In addition to quoting Isaiah, the Savior bracketed that part of his discourse with the command to study Isaiah’s words in their possession.