St. Hilary: A belief that the Son of God is Son in name only, and not in nature, is not the faith of the Gospels and of the Apostles…whence I ask, was it that the blessed Simon Bar–Jona confessed to Him, Thou art the Christ, the Son of the living God?..And this is the rock of confession whereon the Church is built…that Christ must be not only named, but believed, the Son of God. This faith is that which is the foundation of the Church; through this faith the gates of hell cannot prevail against her. This is the faith which has the keys of the kingdom of heaven. Whatsoever this faith shall have loosed or bound on earth shall be loosed or bound in heaven…The very reason why he is blessed is that he confessed the Son of God. This is the Father’s revelation, this the foundation of the Church, this the assurance of her permanence. Hence has she the keys of the kingdom of heaven, hence judgment in heaven and judgment on earth…Thus our one immovable foundation, our one blissful rock of faith, is the confession from Peter’s mouth, Thou art the Son of the living God (Philip Schaff and Henry Wace, Nicene and Post-Nicene Fathers (Grand Rapids: Eerdmans, 1955), On The Trinity, Book VI.36,37; Book II.23; Book VI.20.
Cyril of Alexandria: But why do we say that they are ‘foundations of the earth’? For Christ is the foundation and unshakable base of all things—Christ who restrains and holds together all things, that they may be very firm. Upon him also we all are built, a spiritual household, put together by the Holy Spirit into a holy temple in which he himself dwells; for by our faith he lives in our hearts. But the next foundations, those nearer to us, can be understood to be the apostles and evangelists, those eyewitnesses and ministers of the word who have arisen for the strengthening of the faith. For when we recognize that their own traditions must be followed, we serve a faith which is true and does not deviate from Christ. For when he wisely and blamelessly confessed his faith to Jesus saying, ‘You are Christ, Son of the living God,’ Jesus said to divine Peter: ‘You are Peter and upon this rock I will build my Church.’ Now by the word ‘rock’, Jesus indicated, I think, the immoveable faith of the disciple. Likewise, the psalmist says: ‘Its foundations are the holy mountains.’ Very truly should the holy apostles and evangelists be compared to holy mountains for their understanding was laid down like a foundation for posterity, so that those who had been caught in their nets would not fall into a false faith (Commentary on Isaiah IV.2, M.P.G., Vol. 70, Col. 940).