There is plenty of biblical evidence that might placate a “Bible Only” Protestant Christian.
Expand the discussion to an allegory, using architecture as the theme, citing the following’
the Church
a Foundation
and, a Cornerstone
The Church is the “household” of God, built on the foundation of the Apostles, with Jesus as the cornerstone.
Ephesians 2:19-22
19So then you are no longer strangers and sojourners, but you are fellow citizens with the saints and members of the household of God, 20built upon the foundation of the apostles and prophets, Christ Jesus himself being the cornerstone, 21in whom the whole structure is joined together and grows into a holy temple in the Lord; 22in whom you also are built into it for a dwelling place of God in the Spirit.
If the “foundation” the Church was to be built on was weak, the Church would not survive.
The purpose of a foundation is to hold up and hold together the structure above it. Contrary to our everyday experience the ground is not quite still and in many cases not totally solid. A house which is just plonked down on bare earth is more likely to be cracked or damaged over time by natural forces. A properly-built foundation increases the amount of abuse a house structure can take and remain safe for the people inside it.
Luke 6:47-49
47Every one who comes to me and hears my words and does them, I will show you what he is like: 48he is like a man building a house, who dug deep, and laid the foundation upon rock; and when a flood arose, the stream broke against that house, and could not shake it, because it had been well built. 49*But he who hears and does not do them is like a man who built a house on the ground without a foundation; against which the stream broke, and immediately it fell, and the ruin of that house was great.”
Jesus saw the faith of Peter the strong foundation of rock (see Luke 6:48, above), on which the Church could be built and weather the assault the evil one would place on it Matthew 16:18 - And I tell you, you are Peter, and on this rock I will build my Church, and the gates of Hades shall not prevail against it).
The cornerstone (or foundation stone) concept is derived from the first stone set in the construction of a masonry foundation, important since all other stones will be set in reference to this stone, thus determining the position of the entire structure.
Christ, time and time again, is referred to as the “cornerstone” (of the Church):
Psalm 118:22
The stone which the builders rejected has become the cornerstone.
Acts 4:10-12 (Peter speaking)
10be it known to you all, and to all the people of Israel, that by the name of Jesus Christ of Nazareth, whom you crucified, whom God raised from the dead, by him this man is standing before you well. 11This is the stone which was rejected by you builders, but which has become the cornerstone. 12*And there is salvation in no one else, for there is no other name under heaven given among men by which we must be saved.”
Scripture shows us clearly that Peter IS the foundation, and Christ is the Cornerstone; both a foundation and a cornerstone to allow the Church built by God to stand forever.
Hope this helps
Peace and all Good!