Matthew 16:6-12 The leaven of the Pharisees and the Sadducees is corrupt and corrupting. It is a destructive doctrine they were teaching. This doctrine disintegrates and passes on the process of disintegration. The Pharisees' leaven is still repeated today by people who impose commands on others. The Sadducees teaching of naturalism is a cultic system of beliefs similar to much of what is going on now. The disciples missed the point He was making because they were occupied with only the material matters. They forgot who they following and this showed their lack of faith.
Matthew 16:13-20 The Lord knew the answer before He asked the question. Everyone knew there was something supernatural about Him and the variety of opinions they had only ranked Him among the prophets. Then He narrows the circle to those who had been with Him. Peter's confession is the heart of this passage. "Thou art the Christ," is a Jewish believer's response. They had been looking for the Messiah for generations. Peter is saying the Lord is more than John the Baptist, Jeremiah and all of the great prophets. Peter continues, "The Son of the Living God." The Son of man is truly the Son of God – the King.
The Lord's response: 1st – Peter is blessed because the Father in heaven revealed Christ to Him. He is not rewarded, but blessed with divine illumination. This was revealed through Christ Himself who came to reveal the Father. This truth never left Peter for the rest of His life. 2nd – "Thou art Peter" (petros), a piece of rock, a fragment. He was going to build His Church on "petra" – essential rock. The word "rock" is used of God, never of man in the Bible. Peter was a piece of that rock foundation.
"My Church": He is the Commander of a great called out group of people, a constructive force of this age teaching the Kingdom and holding the keys to interpret and administer God's will. The Church also holds up moral standards to the world. The Church is to be the standards of ethics. The Church teaches the moral standards of life and teaches the will of God.