The central message of this sermon is that Isaiah's prophecy is not just about predicting the future, but rather about conveying God's message and revealing His glory. The preacher highlights how Isaiah's book has a unique structure, mirroring the structure of the Bible as a whole, with 39 chapters focusing on judgment and 27 on comfort. He also explores how Isaiah's perspective jumps back and forth in time, showing that the Messiah's first and second comings can appear as a single event due to the mystery of the church not being fully revealed until the New Testament era. This core message advances the belief that God is actively working through human prophets to convey His message and reveal Himself to humanity throughout history. The takeaway for listeners is that Isaiah's prophecy is not just about predicting events, but about understanding God's character and purposes as revealed through His word.