Several early church fathers believed it was the CONFSSION of Peter? Sources please…
‘And I say unto thee, Thou art Peter, and upon this rock I will build my Church’; that is,
on the faith of his confession. Hereby He signifies that many were on the point of believing, and raises his spirit, and makes him a shepherd…For the Father gave to Peter the revelation of the Son; but the Son gave him to sow that of the Father and that of Himself in every part of the world; and to mortal man He entrusted the authority over all things in Heaven, giving him the keys; who extended the church to every part of the world, and declared it to be stronger than heaven (Philip Schaff, Nicene and Post-Nicene Fathers (Grand Rapids: Eerdmans, 1956), Volume X, Saint Chrysostom, Homilies on the Gospel of Saint Matthew, Homily 54.2-3; pp. 332-334).
Let no one then foolishly suppose that the Christ is any other than the only begotten Son. Let us not imagine ourselves wiser than the gift of the Spirit. Let us hear the words of the great Peter, ‘Thou art the Christ, the Son of the living God.’ Let us hear the Lord Christ confirming this confession, for ‘On this rock,’ He says, ‘I will build my church and the gates of Hell shall not prevail against it.’ Wherefore too the wise Paul, most excellent master builder of the churches, fixed no other foundation than this. ‘I,’ he says, ‘as a wise master builder have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereon. For other foundation can no man lay than that is laid, which is Jesus Christ.’ How then can they think of any other foundation, when they are bidden not to fix a foundation, but to build on that which is laid? The divine writer recognises Christ as the foundation, and glories in this title (Philip Schaff, Nicene and Post-Nicene Fathers (Grand Rapids: Eerdmans, 1953), Volume III, Theodoret, Epistle 146, To John the Economus, p. 318).
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), St. Hilary, On The Trinity, Book VI.36,37; Book II.23; Book VI.20.
He confessed that ‘Christ’ is ‘the Son of the living God,’ and was told, ‘On this rock of sure faith will I build my church’—for he plainly confessed that Christ is true Son (The Panarion of Epiphanius of Salamis (Leiden: Brill, 1994), Books II and III, Haer. 59.7, 6-8,3, pp. 108-109).
Now Christ called this confession a rock, and he named the one who confessed it ‘Peter,’ perceiving the appellation which was suitable to the author of this confession. For this is the solemn rock of religion, this the basis of salvation, this the wall of faith and the foundation of truth: ‘For no other foundation can anyone lay than that which is laid, which is Christ Jesus.’ To whom be glory and power forever (St. Basil of Seleucia, Oratio XXV.4, M.P.G., Vol. 85, Col. 296-297).
Whom do you say that I am?’ Instantly, the Coryphaeus of the apostles, the mouth of the disciples, Peter, ‘Thou art the Christ, the Son of the living God…Upon this faith the Church of God has been founded. With this expectation, upon this rock the Lord God placed the foundations of the Church (Homily of the Nativity. Cited by J. Waterworth S.J., A Commentary (St. Paul of Emesa, London: Thomas Richardson, 1871), p. 148).
This is that firm and immovable faith upon which, as upon the rock whose surname you bear, the Church is founded. Against this the gates of hell, the mouths of heretics, the machines of demons—for they will attack—will not prevail. They will take up arms but they will not conquer (St. John of Damascus, Homily on the Transfiguration, M.P.G., Vol. 96, Col. 554-555).