He changed his name to demonstrate he was 1) correct on the revelation Jesus was the Christ, which would soon be proclaimed throughout the world (the gospel) and 2) that he was going to be used by Jesus to help lay the foundation of the church.
Wrong again.
Here is a more detailed explanation of Matthew 16:13-19 and why Jesus went all the way to Ceasaria Philippi to rename Simon as Rock and to promise him that he will be the rock upon which Jesus will build His Church.
Background:
Caesaria Philipi is around 20 miles ( a rough two days journey up the mountains) from Galillee.
Now why does our Lord go to all that trouble just for this scene?
Caesaria Philipi which used to be called Panneas was dedicated to the Greek god Pan. When Philip Herod became tetrarch of that region he gave it to Augustus Caesar for some favour so it became Ceasaria Philipi, that is, Ceasar’s city from Philip.
In this region is a humongous rock around 500ft long and 200ft high.
On top of this rock is a huge marble temple with an idol of the god Pan. Philip Herod replaced that idol of Pan with the idol of the divine Ceasar Augustus (emperors were considered divine).
To the left of the rock is a cave and in the cave is a deep hole filled with water which is the source of the Jordan river. The pagans believed this to to be the gates of sheol - the doorway to the underworld.
With that scene in mind, let us now read Matthew 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.” **
Comment:
So now we have Jesus standing next to this rock, on top of which, is a temple to a false god (two false gods as a matter of fact) next to which is a cave that is the gate to sheol. He is now saying that He will do something different. He will build the Church of the True God on top of the true rock and that rock is Simon barJonah and the gates of hell will not prevail against it.
We even see here a parallel with the sheep/shepherd motif in the commissioning of Peter in John 21. This area and temple used to be dedicated to Pan, the god of shepherds. Here we have Chist the True God giving the promise to Peter who He will later commission to shepherd His sheep.
Steve Ray also notes the implication of the water in the cave. He comments that when you think of Peter being the rock and the water from this Rock now waters Gods’ people.
Also, since this cave is the origin of the Jordan river where Jesus was baptized and went with His disciples when they went baptizing, you can see in this symbolism the whole salvation theology including that of baptism as a sacrament of incorporation into Christ’s Church.
Another thing, and this is very important, neither Jesus nor the Father made any teaching about Jesus’ true identity and mission. This teaching THEY caused to be pronounced through Peter.
Christ could have gone around proclaiming He is the Son of God but He didn’t. He let that be declared through Peter.
If you notice, even His apostles had no real clue as to who Jesus was. Peter cuts through all that speculation and pronounces the TRUTH about Jesus Christ. Through the ages to this very day, his successors continue to pronounce the truth about who Jesus is and what His mission is all about.