“Having been built on the foundation of the apostles and prophets, Jesus Christ Himself being the chief cornerstone.” (Eph 2:20)
The house of God is built upon the foundation of the apostles and the prophets, Christ Jesus Himself being the cornerstone. The definition of the cornerstone from Wikipedia: “The cornerstone (or foundation stone or setting stone) is the first stone set in the construction of a masonry foundation. All other stones will be set in reference to this stone, thus determining the position of the entire structure.”