We (Presbyterian) were taught that the statement Peter made was the rock, or the foundation.:
He saith unto them, But whom say ye that I am?
Mat 16:16
And Simon Peter answered and said, Thou art the Christ, the Son of the living God. 17
And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in Heaven
Mat 16:18
And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
That's right - Jesus rebukes Peter, because Peter wants Christ without the Cross! He wants salvation with hard work and suffering!
[21] From that time Jesus began to shew to his disciples, that he must go to Jerusalem, and suffer many things from the ancients and scribes and chief priests, and be put to death, and the third day rise again. [22] And Peter taking him, began to rebuke him, saying: Lord, be it far from thee, this shall not be unto thee. [23] Who turning, said to Peter: Go behind me, Satan, thou art a scandal unto me: because thou savourest not the things that are of God, but the things that are of men. [24] Then Jesus said to his disciples: If any man will come after me, let him deny himself, and take up his cross, and follow me. [25] For he that will save his life, shall lose it: and he that shall lose his life for my sake, shall find it.
We (Presbyterian) were taught that the statement Peter made was the rock, or the foundation.:
He saith unto them, But whom say ye that I am? Mat 16:16
And Simon Peter answered and said, Thou art the Christ, the Son of the living God. 17 And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in Heaven Mat 16:18
And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
https://www.blueletterbible.org/kjv/mat/16/18/t_conc_945018
Petros is the word used when Peter is addressed, petra is the word used in reference to the rock that would be built on.
Ironically enough, He turns around almost immediately and rebukes Peter as an adversary, when Peter responds to a statement about Jesus' death.
Matt 16:21 https://www.blueletterbible.org/kjv/mat/16/1/s_945001
That's right - Jesus rebukes Peter, because Peter wants Christ without the Cross! He wants salvation with hard work and suffering!
Matthew 16:21-25