Blalron stated:
Protestants say that the Rock referred to is Jesus.
Actually Blalron, as I shall show, not all non-Catholics say the Rock is Jesus.
Fact #1
Protestant Greek scholars like D.A. Carson and Joseph Thayer admit there is no distinction in meaning between petros and petra in the Koine Greek of the New Testament. [Joseph H. Thayer, Thayer's Greek-English Lexicon of the New Testament (Peabody: Hendrickson, 1996), 507; D.A. Carson, "Matthew," in Frank E. Gaebelein, ed., The Expositor's Bible Commentary (Grand Rapids: Zondervan, 1984), vol. 8, 368.] As it has been pointed out, petra means a 'rock.' It even usually means a 'large rock.' And that's exactly what petros means, too - large rock. It does not mean 'pebble' or 'small stone,' as some have claimed. The Greek word for 'pebble' or 'small stone' is lithos, not petros.
Fact #2
Looking at the Greek, Matthew used the demonstrative pronoun taute, which means 'this very,' when he referred to the rock on which the Church would be built: 'You are Peter, and on taute petra(this very rock), 'I will build My Church.'
Also, when a demonstrative pronoun is used with the Greek word for 'and,' which is 'kai,' the pronoun refers back to the preceding noun. In other words, when Jesus says, 'You are rock, and on this rock I will build My Church,' the second rock He refers to has to be the same rock as the first one. Peter is the rock in both cases.
Jesus could have gotten around it if He'd wanted to. He didn't have to say, 'And(kai) on this rock I will build My Church.' He could've said, 'But(alla) on this rock I will build My Church,' meaning another rock. He would have then had to explain who or what this other rock was. But He didn't do that.
Fact #3
Peter was not a common name in the apostolic age. In fact, it was unheard of. Peter means "Rock" and comes from the Greek "Petras" which is a translation of the Aramaic "Kephas", the language Jesus and the apostles spoke. It is a new name given to him by Jesus as soon as Jesus first approaches this future apostle, Simon in John 1:42: "Then he brought him to Jesus. Jesus looked at him and said, 'You are Simon the son of John; you will be called Cephas'".
We know that Jesus spoke Aramaic because some of his words are preserved for us in the Gospels. Look at Matthew 27:46, where he says from the Cross, 'Eli, Eli, lama sabachthani?' That isn't Greek; it's Aramaic, and it means, 'My God, my God, why have you forsaken me?'
What is Cephas? It is a transliteration of the Aramaic "Kephas", meaning massive rock. We have this name preserved 4 times in Galations and 4 times in 1 Corinthians. The Aramaic for small stone or pebble is evna. In the Old Testament, "Rock" referred exclusively to God alone, and here we have Jesus telling one of his disciples that he is the Rock the second they meet. This is obviously a sign that Jesus has something great in mind for this apostle.
Don't believe the "Petros" argument.. In the apostolic age, Petras and Petros had one and the same meaning (we know this from Greek poetry), and you couldn't name a man with a feminine noun, so to make it fit, the Greek changed Petras to "Petros" for grammatical sake. It was only after this that this Greek noun began to hold dichotomous meanings according to its gender.
And thus, some people (out of ignorance or distaste of Tradition) still hold to the argument that Matthew 16:18 says "You are Petros and upon this Petras, I will build my church", and since today Petros means "small pebble", Jesus was contrasting Peter from Himself in this passage, which is merely pure misunderstanding of the passage taken out of its lingual context.