But you are a chosen race, a royal priesthood, a holy nation, a people for God's own possession, that you may show forth the excellencies of him who called you out of darkness into his marvelous light:
Jesus is a cornerstone, the foundation upon which the church is built, but yet He is also a stumbling stone. The Jews stumble over Him because of the crucifixion. They could not understand the Messiah being crucified and so they stumbled over this stone. He became a rock of offence to them.