Peter was one of Jesus' most important followers. Especially for Catholics, who believe that the Pope is the successor of Peter, the role of Peter in the early church is very significant.
The reading from the gospel according to Matthew tells the familiar story of Jesus’ conversation with his disciples about his identity. Responding to Jesus’ questions, his disciples told Jesus who people were saying he was; then Simon Peter said that Jesus was “the Christ, the Son of the living God.” Jesus blessed him because God had revealed this to him. Then Jesus said to him, “you are Peter [= Rock], and upon this rock I will build my church.” Jesus gave Simon the name Peter, or Rock, to signify that he was the foundation on which his church, the gathering of those who followed Jesus, would be built.
Jesus did not explain exactly how Peter would serve as the foundation of the church. However, the story implies that it was partly a matter of having and expressing the basic faith in Jesus that constitutes the church, i. e., faith that Jesus is the Christ, the Son of the living God. Jesus indicated another element of Peter’s being the foundation of the church by saying to Peter, “I will give you the keys of 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.” Peter will have the keys of the kingdom, apparently an image of the power to bind and loose that is then mentioned.
Binding and loosing is itself an image. The words refer to fastening something with rope, or the like, and unfastening it. Presumably the image refers to prohibiting or permitting something. Later in the gospel of Matthew, Jesus tells his disciples to excommunicate a persistent sinner and repeats, “whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven” (Matt 18:18). Peter will exercise in a special way the decision-making power of the church.
Jesus’ selection of Peter to be the foundation of his church was anticipated by the incident described in the reading from the book of the prophet Isaiah. In this reading Isaiah conveys a message from God to a man named Shebna, who was master of the palace. The message is that God will remove Shebna from his office and replace him with another man named Eliakim. Through Isaiah God says, “I will place the key of the House of David on Eliakim’s shoulder; when he opens, no one shall shut; when he shuts, no one shall open.” Like Peter, Eliakim will receive a key that symbolizes authority, the authority to open and shut. However, Eliakim is only given the key to the royal palace of Judah; Peter receives the keys to the kingdom of heaven.
The reading from the letter of St. Paul to the Romans is a doxology. This doxology concludes Paul’s discussion of the place of Israel in the divine plan in Romans 9-11, and praises God’s mysterious ways. Paul says, “Oh, the depth of the riches and wisdom and knowledge of God! How inscrutable are his judgments and how unsearchable his ways!” Paul says this because he has just been contemplating the way the unbelief of Israel has led to salvation for the Gentiles, whose faith will ultimately lead to the salvation of all Israel. However, God can also be praised in this way for other things. Perhaps Jesus’ choice of Peter as the foundation of the church is one of them.