The Epistles of Cyprian

¹⁰ There is no ground, therefore, dearest brother, for thinking that we should give way to heretics so far as to contemplate the betrayal to them of that baptism, which is only granted to the one and only Church. It is a good soldier's duty to defend the camp of his general against rebels and enemies. It is the duty of an illustrious leader to keep the standards entrusted to him. It is written, “The Lord your God is a jealous God.” We who have received the Spirit of God ought to have a jealousy for the divine faith; with such a jealousy as that wherewith Phineas both pleased God and justly allayed His wrath when He was angry, and the people were perishing.

Why do we receive as allowed an adulterous and alien church, a foe to the divine unity, when we know only one Christ and His one Church? The Church, setting forth the likeness of paradise, includes within her walls fruit-bearing trees, whereof that which does not bring forth good fruit is cut off and is cast into the fire. These trees she waters with four rivers, that is, with the four Gospels, wherewith, by a celestial inundation, she bestows the grace of saving baptism. Can any one water from the Church's fountains who is not within the Church? Can one impart those wholesome and saving draughts of paradise to any one if he is perverted, and of himself condemned, and banished outside the fountains of paradise, and has dried up and failed with the dryness of an eternal thirst?