"Every one then who hears these words of mine and does them will be like a wise man who built his house upon the rock [petra];
and the rain fell, and the floods came, and the winds blew and beat upon that house, but it did not fall, because it had been founded on the rock [petra].
And every one who hears these words of mine and does not do them will be like a foolish man who built his house upon the sand; and the rain fell, and the floods came, and the winds blew and beat against that house, and it fell; and great was the fall of it." Matt. 7: 24-27; see also Luke 6:48
If you do a search of the word "rock" in the Old Testament, you will soon discover that it is often used to describe God. God is a rock. The Greek words for rock "petra" and "lithos" are also used for Christ Himself:
"for they drank from the spiritual rock [petra] that accompanied them, and that rock was Christ." I Cor. 10:4
"The stone [lithos] which the builders rejected, the same is become the head of the corner." Matt. 21: 42; Mark 12: 10; Luke 20: 17; Acts 4: 11; I Peter 2: 6, 7
Jesus gave Peter the title of rock, a description of Himself:
And I tell you that you are Peter, and on this rock [petra] I will build my church, and the gates of Hades will not overcome it. Matt. 16: 18
And when Jesus beheld him, he said, Thou art Simon the son of Jona: thou shalt be called Cephas, which is by interpretation, a stone [petros]. John 1: 42
His other disciples are considered part of the stone foundation.
And are built upon the foundation of the apostles and prophets, Jesus Christ himself being the chief corner stone; Eph. 2: 20
So when the Jesus talks about the rock, He is describing the authority of the Kingdom, both Himself and Peter, His chief administrator and Prince of His Apostles, as well as the other Apostles. All of these leaders are the foundation of His church. Yet they are one stone foundation, not many. One.
When Christ tells His disciples that a wise man builds his house upon the rock, He is speaking of the foundation of not only Christ Himself, but of Peter and the Apostles. They are all the rock foundation.
Why would Christ choose the image of sand as a false and foolish foundation? Why not mud or water or air? No, Christ chose the image of little rocks. Little false rocks--many, many of them. What could be these little rocks?
It seems to me a fairly easy guess. Protestantism brought in the idea that the church isn't one, organized body. There are now thousands of little foundations in denominationalism and even more people who reject church altogether who have become little independent foundations. If you call yourself a Christian but build your foundation upon some other rock than the rock Christ gave us in Peter and the Apostles, you are in for a big shock when a spiritual storm blows.
Jesus knew that this rock foundation of Himself and the Apostles would offend the independent-minded, those who wish to be their own church and their own spiritual authority.
I lay in Zion, "a stone [lithos] that causes men to stumble and a rock [petra] that makes them fall." I Peter 2: 8; Rom. 9: 33 See also: Matt. 21: 44; Luke 20:18.
Build your foundation on The Rock of Jesus and Peter. You will be safe.