Letter of Saint Athanasius to His Flock (4th Century A.D.)
"May God console you! ... What saddens you ... is the fact that others have occupied the churches by violence, while during this time you are on the outside. It is a fact that they have the premises --- but you have the Apostolic Faith. They can occupy our churches, but they are outside the true Faith. You remain outside the places of worship, but the Faith dwells within you. Let us consider: what is more important, the place or the Faith? The true Faith, obviously. Who has lost and who has won in the struggle --- the one who keeps the premises or the one who keeps the Faith?
True, the premises are good when the Apostolic Faith is preached there; they are holy if everything takes place there in a holy way ...
You are the ones who are happy; you who remain within the Church by your Faith, who hold firmly to the foundations of the Faith which has come down to you from Apostolic Tradition. And if an execrable jealousy has tried to shake it on a number of occasions, it has not succeeded. They are the ones who have broken away from it in the present crisis.
No one, ever, will prevail against your Faith, beloved Brothers. And we believe that God will give us our churches back some day.
Thus, the more violently they try to occupy the places of worship, the more they separate themselves from the Church. They claim that they represent the Church; but in reality, they are the ones who are expelling themselves from it and going astray.
Even if Catholics faithful to Tradition are reduced to a handful, they are the ones who are the true Church of Jesus Christ."
(Coll. selecta SS. Eccl. Patrum, Caillau and Guillou, Vol. 32, pp. 411-412)
See Also : www.ccel.org/ccel/athanasius/incarnation.toc.html