2 Nor does what you have described in your letters disturb us, dearest brother, that the Novatians re-baptize those whom they entice from us, since it does not in any wise matter to us what the enemies of the Church do, so long as we ourselves hold a regard for our power, and the steadfastness of reason and truth. For Novatian, after the manner of apes— which, although they are not men, yet imitate human doings— wishes to claim to himself the authority and truth of the Catholic Church, while he himself is not in the Church; nay, moreover, has stood forth hitherto as a rebel and enemy against the Church.
For, knowing that there is one baptism, he arrogates to himself this one, so that he may say that the Church is with him, and make us heretics. But we who hold the head and root of the one Church know, and trust for certain, that nothing is lawful there outside the Church, and that the baptism which is one is among us, where he himself also was formerly baptized, when he maintained both the wisdom and truth of the divine unity. But if Novatian thinks that those who have been baptized in the Church are to be re-baptized outside— without the Church— he ought to begin by himself, that he might first be re-baptized with an extraneous and heretical baptism, since he thinks that after the Church, yea, and contrary to the Church, people are to be baptized without.
But what sort of a thing is this, that, because Novatian dares to do this thing, we are to think that we must not do it! What then? Because Novatian also usurps the honour of the priestly throne, ought we therefore to renounce our throne? Or because Novatian endeavours wrongfully to set up an altar and to offer sacrifices, does it behoove us to cease from our altar and sacrifices, lest we should appear to be celebrating the same or like things with him? Utterly vain and foolish is it, that because Novatian arrogates to himself outside the Church the image of the truth, we should forsake the truth of the Church.
Source: The Epistles of Cyprian (New Advent)