And I say to thee: That thou art Peter; and upon this rock I will build my church, and the gates of hell shall not prevail against it.”[Matthew 16:18]
The Second Council of Constantinople, Sentence against the “Three Chapters”: “These matters having been treated with thorough-going exactness, we bear in mind what was promised about the holy church and him who said that the gates of hell will not prevail against it (by these we understand the death-dealing tongues of heretics); we also bear in mind what was prophesied about the church by Hosea when he said, I shall betroth you to me in faithfulness and you shall know the Lord; and we count along with the devil, the father of lies, the uncontrolled tongues of heretics and their heretical writings, together with the heretics themselves who have persisted in their heresy even to death.”
Pope St. Leo IX, Encyclical “In terra pax hominibus”: “The holy Church built upon a rock, that is Christ, and upon Peter or Cephas, the son of John who first was called Simon, because by the gates of Hell, that is, by the disputations of heretics which lead the vain to destruction, it would never be overcome; thus Truth itself promises, through whom are true, whatsoever things are true: “The gates of hell will not prevail against it” [Matt. 16:18]. The same Son declares that He obtained the effect of this promise from the Father by prayers, by saying to Peter: “Simon, behold Satan etc.” [ Luke 23:31]. Therefore, will there be anyone so foolish as to dare to regard His prayer as in anyway vain whose being willing is being able? By the See of the chief of the Apostles, namely by the Roman Church, through the same Peter, as well as through his successors, have not the comments of all the heretics been disapproved, rejected, and overcome, and the hearts of the brethren in the faith of Peter which so far neither has failed, nor up to the end will fail, been strengthened?”[DENZ 351]
St. Thomas Aquinas, Catena Aurea,Gospel of Matthew, Introduction: “You, the rightful heir to this faith and testimony, most holy Father, and your mind is religiously watchful, to let the light of such great wisdom pervade the hearts of the faithful, and refute the madness of heretics, which are rightly called the ‘gates of hell.'”
St. Augustine, A Sermon to Catechumens on the Creed, #14: “It follows after commendation of the Trinity, The Holy Church. God is pointed out, and His temple. For the temple of God is holy, says the Apostle, which (temple) are you. This same is the holy Church, the one Church, the true Church, the Catholic Church, fighting against all heresies: fight, it can: be fought down, it cannot. As for heresies, they went all out of it, like as unprofitable branches pruned from the vine: but itself abides in its root, in its Vine, in its charity. ‘The gates of hell shall not prevail against it.’”
St. John Cassian, On the Incarnation Bk. 3, Ch. 14: “But what are the other words which follow that saying of the Lord’s, with which He commends Peter? And I, said He, say unto you, that you are Peter and upon this rock I will build My Church. Do you see how the saying of Peter is the faith of the Church? He then must of course be outside the Church, who does not hold the faith of the Church. And to you, says the Lord, I will give the keys of the kingdom of heaven. This faith deserved heaven: this faith received the keys of the heavenly kingdom. See what awaits you. You cannot enter the gate to which this key belongs, if you have denied the faith of this key. And the gate, He adds, of hell shall not prevail against you. The gates of hell are the belief or rather the misbelief of heretics.”
St. Francis de Sales, The Catholic Controversy, Part II, Art. VI, Ch. 13: “So when S. Peter was placed as foundation of the Church, and the Church was certified that the gates of hell should not prevail against it, — was it not enough to say that S. Peter, as foundation-stone of the ecclesiastical government and administration, could not be crushed and broken by infidelity or error, which is the principal gate of hell? For who knows not that if the foundation be overthrown, if that can be sapped, the whole building falls. In the same way, if the supreme acting shepherd can conduct his sheep into venomous pastures, it is clearly visible that the flock is soon to be lost. For if the supreme acting shepherd leads out of the path, who will put him right? if he stray, who will bring him back ?
In truth, it is necessary that we should follow him simply, not guide him; otherwise the sheep would be shepherds. And indeed the Church cannot always be united in General Council, and during the first three centuries none were held. In the difficulties then which daily arise, to whom could one better address oneself, from whom could one take a safer law, a surer rule, than from the general head, and from the vicar of Our Lord? Now all this has not only been true of S. Peter, but also of his successors; for the cause remaining the effect remains likewise. The Church has always need of an infallible confirmer, to whom she can appeal; of a foundation which the gates of hell, and principally error, cannot overthrow; and has always need that her pastor should be unable to lead her children into error. The successors, then, of S. Peter all have these same privileges, which do not follow the person but the dignity and public charge.”
My Comment: To some people, “the gates of hell” is an uncertain term that may have different meanings. The purpose of this is to show that heretics and their heresies are actually the Gates of Hell. This is taught in Councils, by Popes, by Church Fathers and Doctors. This is significant because is proves that a heretic cannot occupy the Papal Throne. Our Lord’s Words to St. Peter show that the Gates of Hell (heretics/heresies) and the Rock (St. Peter/the Popes) are distinct from each other. Therefore, the Pope cannot be a heretic according to Our Lord.