Ephesians 2:20

Being built upon the foundation of the apostles and prophets, Christ Jesus himself being the chief corner stone.

The foundation of the apostles and prophets ... There are five foundations of the Christian faith mentioned in the New Testament: (1) The foundational teaching is composed of the teachings of Christ delivered through the apostles and prophets of the new dispensation (Matthew 7:24-26). (2) The foundational fact is that Jesus Christ is the Son of the living God (Matthew 16:13-20). (3) The foundation person is Jesus Christ our Lord (1 Corinthians 3:11). (4) The foundational personnel was made up of the apostles and prophets of the New Testament, as revealed here. (5) The foundational doctrines of Christianity (six of these) are enumerated in Hebrews 6:1,2.

Significantly, many different metaphors are needed to set forth the many facets of Christ's relationship to his people on earth. He is called the bridegroom, the lord of the vineyard, the foundation, the cornerstone, the good shepherd, the true vine, the door of the sheep, the pioneer, the forerunner, the head of the body, etc., etc.

Corner stone ... In this verse, perhaps the ancient cornerstone was the basis of the metaphor. It was more than what is usually called a cornerstone now. Several lines of the building were bound together, completed and held together by the cornerstone. For more extended comment on this subject, see my Commentary on Romans 9, "Christ the Living Stone."