He said to them, "But who do you say that I am?" Simon Peter replied, "You are the Christ, the Son of the living God."
Peter correctly answers the most important question of our times: "Who is Jesus?" It was important for those who lived with Him during His earthly ministry. It is important for all those who have lived since His time. He is the central focus of God's revelation. And He is the turning point of human history. Answering this question is important both from God's perspective, and from ours.
Peter's understanding shows that He knew Jesus as more than just a human being. And having walked with Him, spoken to Him, learned from Him, given up all to be His disciple, and seen Him change everything known about God and what God wants in the human heart, Peter saw something much more than humanity in Jesus. He knew Jesus as the Messiah of Old Testament prophecy and as the very God of Israel come to earth as a human being. This confession was profound.
Jesus was so moved by it that He told Peter that what He had observed and discovered would be the foundation for all future belief in Him in the church. Peter's confession is the foundational necessity of orthodoxy. Anyone who wants to teach a simple, human Jesus then is denying the faith and is not a part of Jesus' church as He defined it.
Jesus also knew that with this knowledge would come incredible opportunity as the power of God attended the message of the gospel. That is why "the keys of the kingdom" would come with the proclamation of Jesus as Messiah and God. And that is why Jesus cautioned His disciples to hold on to this message until the proper time would come to proclaim Him.