Mt 16:13-23
13When Jesus went into the region of Caesarea Philippi he asked his disciples, “Who do people say that the Son of Man is?” 14They replied, “Some say John the Baptist, others Elijah, still others Jeremiah or one of the prophets.” 15He said to them, “But who do you say that I am?” 16Simon Peter said in reply, “You are the Messiah, the Son of the living God.” 17Jesus 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.
18And 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. 19I 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.” 20Then he strictly ordered his disciples to tell no one that he was the Messiah. 21From that time on, Jesus began to show his disciples that he must go to Jerusalem and suffer greatly from the elders, the chief priests, and the scribes, and be killed and on the third day be raised. 22Then Peter took him aside and began to rebuke him, “God forbid, Lord! No such thing shall ever happen to you.” 23He turned and said to Peter, “Get behind me, Satan! You are an obstacle to me. You are thinking not as God does, but as human beings do.”
Upon the Rock: Palestine is a land of mountains and precipitous crags—rocks are a common sight. When the image of rock (Hebrew sur) is used, it suggests a stronghold from which one can resist attack by enemies. The Old Testament uses the title to describe God and his attributes. Yahweh is the rock of Israel (Is 30:29), the righteous and faithful rock (Dt 32:4).
In the New Testament, Paul applies the title to Christ (1 Cor 10:4). Paul refers to a rock from which water issued, quenching the thirst of the Israelites in the desert (Ex 17:6-7). For Paul the rock is Christ. As Yahweh was the Rock of his people, so Christ is the true Rock that accompanies his people in the journey. He is the true source of living water.
When Jesus tells Simon that he is the rock on which Jesus will build his Church, the image given is one of security, stability, and strength. Jesus is like a wise man who builds his house on rock, so that no amount of buffeting by the wind can make it collapse (see Mt 7:24-25). But Simon becomes petra (Greek for “rock”) through grace, by the fact that he is given a revelation of Jesus as the Messiah, the Son of the living God. His being rock depends on this confession. Peter can only be a rock if he depends on Jesus, the true Rock.