+ Mt 16: 13-19
When Jesus went into the region of Caesarea Philippi he asked his disciples, “Who do people say that the Son of Man is?”
They replied, “Some say John the Baptist, others Elijah, still others Jeremiah or one of the prophets.”
He said to them, “But who do you say that I am?”
Simon Peter said in reply, “You are the Messiah, the Son of the living God.”
Jesus said to him in reply, “Blessed are you, Simon son of Jonah. For flesh and blood has not revealed this to you, but my heavenly Father.
And so I say to you, you are Peter, and upon this rock I will build my church, and the gates of the netherworld shall not prevail against it.
I will give you the keys to the kingdom of heaven. Whatever you bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven.”
The New American Bible
The Catechism of the Catholic Church
440 Jesus accepted Peter’s profession of faith, which acknowledged him to be the Messiah, by announcing the imminent Passion of the Son of Man. He unveiled the authentic content of his messianic kingship both in the transcendent identity of the Son of Man “who came down from heaven”, and in his redemptive mission as the suffering Servant: “The Son of Man came not to be served but to serve, and to give his life as a ransom for many.” Hence the true meaning of his kingship is revealed only when he is raised high on the cross. Only after his Resurrection will Peter be able to proclaim Jesus’ messianic kingship to the People of God: “Let all the house of Israel therefore know assuredly that God has made him both Lord and Christ, this Jesus whom you crucified.”
Chair of Peter
The feasts thus became associated with an abstract understanding of the “Chair of Peter”, which by synecdoche signifies the episcopal office of the Pope as Bishop of Rome, an office considered to have been first held by Saint Peter, and thus extended to the diocese, the See of Rome.