(Infallible Roman Catholic Pope Saint Gregory I, the Great, [Friday, September 3, 590 - Monday, March 12, 604], Homily on Ezechiel, 7; cited by Saint Thomas Aquinas, O.P., Summa Theologica, Part II-II, Question 43, Article 7.)

Let us consider: what is more important, the place or the Faith? The True Faith, obviously.  Who has lost and who has won in this struggle - the one who keeps the premises, or the one who keeps the Faith?.... 

Even if Catholics faithful to Tradition are reduced to a handful, they are the ones who are the True Church of Jesus Christ.”

(Patriarch Saint Athanasius [b. Alexandria, Egypt 296 A.D. - d. Alexandria, Egypt on Wednesday, May 2, 373A.D.], Patriarch of Alexandria, Egypt, Father of Orthodoxy in the Catholic Church, “Coll. Selecta SS. Eccl. Patrum.,” Caillu and Guillou, Volume 32, pp 411-412; emphasis added.)

Whenever it becomes necessary to expose statements which disguise some suspected error or danger under the veil of ambiguity, one must denounce the perverse meaning under which the error opposed to Catholic Truth is camouflaged.”

(Infallible Roman Catholic Pope Pius VI, Giovanni Angelo Braschi [Wednesday, February 15, 1775 - Thursday, August 29, 1799], using his Infallible Ordinary Magisterium, Promulgated his Infallible Encyclical “Auctorem Fidei,” Thursday, August 28, 1794, ¶ 6; emphasis added).

Wherefore, We may no longer keep silence, lest We should seem to fail in Our most Sacred Duty, and lest the kindness that, in the hope of wiser counsels, We have hitherto shown them, should be set down to lack of diligence in the discharge of Our Office.” 

(Infallible Roman Catholic Pope Saint Pius X, Giuseppe Sarto [Tuesday, August 4, 1903 - Thursday, August 20, 1914], Encyclical Pascendi Dominici Gregis, On the Doctrine of the Modernists, Sunday, September 8, 1907.)

For that holy and prudent man well knew that true piety admits no other rule than that whatsoever things have been faithfully received from our Fathers the same are to be faithfully consigned to posterity.

It is our duty to follow Religion, not to make Religion follow us. The proper characteristic of Christians is not to impose their own beliefs or observances upon posterity, but to preserve and keep what we have received from those who went before us. What then was the issue of the whole matter? What but the usual and customary one? 

Antiquity was retained, novelty [i.e. change] was rejected” 

(Father Saint Vincent of Lerins, [b. Toul, France, c. 400 A.D. - d. Island of Lerins, c. 450 A.D.], A Commonitory [an aid to memory] for the Antiquity and Universality of the Catholic Faith Against the Profane Novelties of All Heresies, Chapter VI, ¶ 16; emphasis added).

Wherefore, just as they may not institute another church, so neither may they deliver another faith, nor institute other sacraments...”
(Saint Thomas Aquinas, O.P., Summa Theologica, Part III, Question 64, Article 2, Reply to Objection 3; emphasis added).

On this was the Church founded; and if anyone departs from this, he neither is, nor any longer ought to be called, a Christian.”

(Patriarch Saint Athanasius [b. Alexandria, Egypt 296 A.D. - d. Alexandria, Egypt on Wednesday, May 2, 373A.D.], Patriarch of Alexandria, Egypt, Father of Orthodoxy in the Catholic Church, Letter to Serapion of Thmuis, 359 A.D.).

But we are not permitted to believe whatever we choose, nor to choose whatever someone else has believed.  We have the Apostles of God as authorities, who did not themselves of their own will choose what they would believe, but faithfully transmitted to the nations the teaching received from Christ. 

So, even if ‘an Angel from Heaven’ should preach otherwise, he shall be called anathemaX(Saint Paul, Epistle to the Galatians 1:8.).” 

(Bishop Saint Isidore of Seville, Spain, [b. Cartagena, Spain 560 A.D. - d. Seville, Spain, 636 A.D.], Doctor of the Catholic Church, Etymologies, 8, 3; emphasis added.)

“Do not be one of those timourous physicians who like their tranquility more than the saving of the sick... 

Even though Salome should dance before Herod, should ask for John's head and should obtain it from the detestable King, John's duty is to cry out: NON LICET! [It is not permitted!].”

(Bishop Saint Ivo of Chartres, a.k.a. Yves, I’ve, Yvo  [b. Beauvais, France or Auteuil, France, c. 1040 A.D. - d. Chartres, France, Tuesday, May 30, 1116 A.D.], Bishop of Chartres [1090 A.D. - Tuesday, May 30, 1116 A.D.], Letter # 24, To Bishop Hugh of Lyons, October, 1094 A.D.)

“Care must especially be had that that [Faith] be held, which was believed everywhere, always, and by all.”

(Father Saint Vincent of Lerins, A Commonitory [an aid to memory] for the Antiquity and Universality of the Catholic Faith Against the Profane Novelties of All Heresies, Chapter 3; emphasis added.)