Shortly before the transfiguration Jesus asked His disciples who they thought He was.

Mat 16:16  Simon Peter answered and said, “You are the Christ, the Son of the living God.”
Mat 16:17  Jesus answered and said to him, “Blessed are you, Simon Bar-Jonah, for flesh and blood has not revealed this to you, but My Father who is in heaven.

It is interesting to note that at this point in time it was not at all obvious to the disciples who Jesus was.  His true identity was something that the Father had to reveal.  The next verse is the one we will focus on.

Mat 16:18  And I also say to you that you are Peter [petros], and on this rock [petra] I will build My church, and the gates of Hades shall not prevail against it.

What did Jesus mean by this?  Was He saying, as the Catholic Church teaches, that Jesus would build His church on the apostle Peter?

Let’s first take a look at the Greek.  “Peter” is translated from the Greek petros, and “rock” from the Greek petra.

According to the Greek-English Lexicon by Liddell and Scott, petros means stone and petra means rock.  The lexicon can be found online here:

https://archive.org/stream/greekenglishlex00lidduoft#page/1206/mode/2up

Here are its entries for petros and petra.  Screen shots from the lexicon can be found in the appendix at the end of this article.

Petra

Petra is a rock, such as run out from the beach, a ledge or shelf of rock.  A rock, i.e. a rocky peak or ridge.  There is no example, in good authors, of petra in the sense of petros, a stone.  Petras are not loose stones, but masses of live rock torn up and hurled by giants.

Petros

Petros is a stone and thus distinguished from petra.

According to the lexicon, the petros means stone and petra means rock.  The Catholic Church agrees that in Attic Greek (ancient Greek 500-300 BC) this is the case; however, it argues that in the Greek of Christ’s time, Koine Greek (common Greek 300 BC – 600 AD), both petros and petra mean rock.  (In today’s modern Greek, petros means Peter, petra means stone, and vrachos means rock.)

The exact meaning of petros at the time of Christ doesn’t really matter, as the meaning of Matthew 16:18 can be determined without this.

Peter’s name “Petros” was given to him by Jesus.

Joh 1:42  And he brought him to Jesus. Now when Jesus looked at him, He said, “You are Simon the son of Jonah. You shall be called Cephas” (which is translated, A Stone [petros]).

Let’s look at verse 18 again.

Mat 16:18  And I also say to you that you are Peter [petros], and on this rock [petra] I will build My church, and the gates of Hades shall not prevail against it.

When Jesus said, “I also say to you that you are Peter [petros]”, there is no doubt that Jesus was talking directly to Peter.  But what about the next phrase, “and on this rock [petra] I will build My church”?  Was Jesus still referring to Peter or Himself?

Surely, if Jesus had meant that He would build his church on Peter He would have said, “and on this Peter [petros] I will build My church” or “and on you I will build My church”.  While this is a persuasive argument, it is not conclusive.

The clincher is found in 1 Corinthians 10:4 where petra is identified as Jesus Christ.

1Co 10:4  and all drank the same spiritual drink. For they drank of that spiritual Rock [petra] that followed them, and that Rock [petra] was Christ.

Using Scripture we see that the Bible uses petros as a name for Peter (John 1:42) and petra as a name for Jesus Christ (1 Corinthians 10:4).  Thus, using Scripture to interpret Scripture we see that Jesus referred to Himself when He said, “and on this rock [petra] I will build My church”.

This is corroborated in Ephesians 2:20 which states that Jesus Christ is the chief cornerstone of the household of God.

Eph 2:19  Now, therefore, you are no longer strangers and foreigners, but fellow citizens with the saints and members of the household of God,
Eph 2:20  having been built on the foundation of the apostles and prophets, Jesus Christ Himself being the chief cornerstone,

Conclusion

Using John 1:42 and 1 Corinthians 10:4 to interpret Matthew 16:18 it is clear that Jesus referred to Himself when He said, “and on this rock [petra] I will build My church”.

Appendix

Petra

Petra is a rock, such as run out from the beach, a ledge or shelf of rock.  A rock, i.e. a rocky peak or ridge.  There is no example, in good authors, of petra in the sense of petros, a stone.  Petras are not loose stones, but masses of live rock torn up and hurled by giants.

Petros

Petros is a stone and thus distinguished from petra.