Timeo Dominum transeuntem - Augustine of Hippo

Temporibus enim nostris venit imperator in urbem Romam: ibi est templum imperatoris, ibi est sepulcrum piscatoris. Itaque ille ad deprecandam a Domino salutem imperator pius atque christianus non perrexit ad templum imperatoris superbum, sed ad sepulcrum piscatoris, ubi humilis ipsum piscatorem imitaretur, ut tunc respectus aliquid impetraret a Domino, quod superbiens imperator mereri non posset.

The Catholic faith, … I now realized could be maintained without presumption. This was especially true after I had heard one or two parts of the Old Testament explained allegorically—whereas before this, when I had interpreted them literally, they had “killed” me spiritually.

God is one, and the Church is a unity; only unity can respond to him who is one. But there are some people why say, “Yes, that certainly was the case. The Church spread among all nations did respond to him, bearing more children than did the wedded wife. It responded to him in the way of his strength, for it believed that Christ had risen. All nations believed in him. But that Church which was drawn from all nations no longer exists: it has perished.”
So say people who are not within the Church. What an impudent assertion! The Church does not exist because you are not in it? Be careful lest such an attitude result in your not existing yourself, for the Church will be here even if you are not. But the Spirit of God anticipated this abominable, detestable assertion, this claim full of presumption and falsehood, a claim with nothing to support it, illumined by no spark of wisdom, seasoned by no salt. God’s Spirit anticipated this empty, unfounded, foolhardy and pernicious proposition and seemingly refuted it in advance by proclaiming that the Church is united by the gathering of the people together into one, and kingdoms to serve the Lord.