The Lord asked, "Whom shall I send, and who will go for us?" Isaiah answered the call, "Here am I; send me." As recorded in Abraham 3:27, this is identical to the words spoken by the Savior in the premortal council as He accepted the call to perform the Atonement as Savior of mankind: "Here am I, send me." Isaiah was willing to make whatever sacrifice was necessary to fulfill his calling as prophet.
The Lord then instructed Isaiah: "Go and tell this people—Hear ye indeed, but they understood not; and see ye indeed, but they perceive not. Make the heart of this people fat, and make their ears heavy, and shut their eyes—lest they see with their eyes, and hear with their ears, and understand with their heart, and be converted and be healed." The Lord explained that the people in Jerusalem were not ready or worthy to be told everything in plain language. Isaiah would be prophesying at a time when Israel would be destroyed.
These verses explain why many people today find it difficult to understand the words of Isaiah. Isaiah was simply magnifying his calling as instructed by the Lord. He had been told to make his writings and teachings opaque—without absolute transparency. But, as Nephi would later explain, Isaiah’s prophecies would become clear to those who have "ears to hear."