The central message of this sermon is that the most fundamental and crucial question to ask oneself is "Who do you say Jesus is?" The answer to this question determines one's eternal destiny, as it either affirms faith in Jesus as the Christ of God or rejects Him. The sermon emphasizes that believing anything about Jesus is not enough; one must specifically affirm His unique identity as the anointed one, the chosen one, and the identified one sent by God. This affirmation is what ensures that one's name is written in the book of life, securing admission into heaven and avoiding the lake of fire. The sermon encourages listeners to take this question seriously and respond with faith, affirming Jesus as the Christ of God, which is the essential step towards salvation and eternal life.