Jesus responded to Peter’s confession by teaching him new truths about his plans. The first concerns how Peter knew so much about Jesus. Maybe Peter had imagined that he had worked it out himself, that over the last few months he had been thinking hard about Jesus and now he understood. It is interesting that Jesus does not claim to have revealed those details about himself. Instead he links the instruction to the Heavenly Father. This does not mean that Jesus was not involved in teaching Peter, nor does it mean that somehow Peter was taught heavenly truths without the Holy Spirit. Instead we have an example here of how the Trinity works in harmony to communicate their intentions to the apostles, and then through them to us.
The way that Jesus speaks to Peter here is striking because it is possible that he is saying that the old Simon has now become the new Peter. Jesus first calls him by his old name and then says to him that he now is Peter who has become a very different person from what he was when he first met Jesus.
What did Jesus mean when referred to a rock? There are three main views about it. One is that Peter himself is the rock, which is what Roman Catholics teach. The second view is that Peter’s confession of Jesus is the rock that he uses to build his church. And the third view is that Jesus is referring to himself as the rock.
Personally I would say that Jesus’ words point back to the conversation that he had with Peter. The rock is the words of the confession that Peter made when he said that Jesus was the Son of the living God. The confession is a rock because it is true. We can see that the confession is reliable because it is connected to the truth about Jesus who is both God and man (the Son of the living God and the Messiah). The other opinions that were expressed by different people were not rocks because they were untrue, which meant that no one could build anything on them.