Jesus continues speaking and uses the confession just uttered by Peter to explain that the truth contained in that confession would serve as the theological and spiritual foundation for an institution that He intended to bring into being. Addressing Peter again, Jesus says: “You are Peter, and upon this rock I will build My church...” (v. 18) In the Greek, this phrase reads: “You are Petros (“Rock”) and upon this petra (“rocky ledge” or “bedrock”) I will build My church...”
Much has been written about this statement; some have insisted that Jesus is bestowing upon Peter a unique status among the others. There's no denying that Peter was an important figure in the early Church, but there is no evidence that he was viewed as one having a unique authority among the other apostles. Peter and the other apostles were not the foundation of the Church, as we will show clearly in a few minutes; but their teaching was the foundation for the Church. This is what Jesus means.
The correct interpretation of this statement begins with a recognition that Jesus is using a play on words to draw the connection between Peter's recent confession and the nature of the Church that soon would be formed. The truth represented in Peter's confession of Jesus as “the Christ, the Son of the living God,” would serve as the solid doctrinal foundation upon which Jesus would erect a spiritual house. That spiritual house, consisting of the redeemed, would bear the characteristics of the foundation. In other words, Jesus Himself, His teaching and what is taught about Him, would determine the nature of the Church; only those who embraced the truth represented in Peter's confession would be or could be part of Christ's institution.
Hope you brought your flameproof clothing for when our Roman Catholc associates see this posting.
Meanwhile, the doctrine of "Render unto Ceasar" is related to secular issues such as the administration of law (marriage and family life included), politics, economics and sociology -- secular matters that religion makes a business of and interferes with; but has no business being in.