I’ve had the conversation several times with Bible-believing Christians on Mt. 16:18 and time and time again they’ll claim that we have to understand the Greek text of what is meant by “rock.” Naturally, they attempt to explain that there are two different forms of rock in the Greek and the reference to Peter is “Petros.” The problem with this assertion is that the Gospels are a translation of the actual language of Jesus which is Aramaic In my experience, once it’s explained that Aramaic has no gender application in their language and that the Greek language forces a user to change Petras to Petros when making it a name for a man, even if there is no agreement on the theological implications, the position of the authority given to Peter is an argument with good Scriptural grounding.
Since appealing to tradition isn’t convincing to a Bible-believing Christian, to make the argument of Petrine authority, one has to appeal to the Holy Scriptures explicitly. Now, a great application at this point is an attempt to frame the Gospel passage within a historical context; however, generally, there is some sort of the premise of a great apostasy—basically Luther’s position; something went wrong—so an appeal to scripture will be most affective. Some Bible-believing Christians will be receptive to a historic argument, but many will simply not accept anything outside of the Bible as authority. However, found in the Old Testament is the understanding of what the authority of the keys means in ancient Israel with royal authority.
In the book of the Prophet Isaiah 22:15-23 exegetes find an explanation that the master of the palace is the one who holds the keys of the kingdom:
15_Thus says the Lord GOD of hosts, “Come, go to this steward, to Shebna, who is over the household, and say to him: 16 What have you to do here and whom have you here, that you have hewn here a tomb for yourself, You who hew a tomb on the height, and carve a habitation for yourself in the rock? 17 Behold, the LORD will hurl you away violently, O you strong man. He will seize firm hold on you, 18 and whirl you round and round, and throw you like a ball into a wide land; there you shall die, and there shall be your splendid chariots, you shame of your master’s house. 19 I will thrust you from your office, and you will be cast down from your station. 20 In that day I will call my servant Eliakim the son of Hilkiah, 21 and I will clothe him with your robe, and will bind your belt on him, and will commit your authority to his hand; and he shall be a father to the inhabitants of Jerusalem and to the house of Judah. 22 And I will place on his shoulder the key of the house of David; he shall open, and none shall shut; and he shall shut, and none shall open. 23 And I will fasten him like a peg in a sure place, and he will become a throne of honor to his father’s house._(Is 22:15–24.).
Now, let examine that language with Matthew’s Gospel which is written exclusively for a Jewish audience:
Matthew 16:19 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.”
Isaiah puts Matthew’s scriptural passage within the context that is framed with the history and culture of ancient Judaism. Now one can frame the authority of St. Peter, as the first pope—the Key Holder of Christ’s authority on earth in Mt. 16:18 within the context of the Old Testament.
Finally, if there is some discrepancy with the Bible-believing Christian appealing to the assertion that the Gospel of Matthew is the only text to have this particular part in its narrative. Naturally, the emphasis is that he speaking to an audience that would receptive and understanding of this specific imagery. Furthermore, all Holy Scripture is inerrant, so whether it’s only found in one of the Gospels isn’t a credible objection.