31. said: "In the third place, also, He calls the madness of persecutors in like manner by this name, ‘Ye generation of vipers, how can ye escape the damnation of hell? Wherefore, behold, I send unto you prophets, and wise men, and scribes; and some of them ye shall kill and crucify; and some of them shall ye scourge in your synagogues, and persecute them from city to city: that upon you may come all the righteous blood shed upon the earth, from the blood of righteous Abel unto the blood of Zacharias, son of Barachias, whom ye slew between the temple and the altar.’ Are they then really the sons of vipers according to the flesh, and not rather serpents in mind, and three-tongued malice, and deadliness of touch, and burning with the spirit of poison? They have truly become vipers, who by their bites have vomited forth death against the innocent people."

32. answered: If I were to say that this is said of men of character like unto yourselves, you would reply, "Prove it." What then, have you proved it? Or if you think that it is proved by the mere fact of its being uttered, there is no need to repeat the same words. Pronounce the same judgment against yourselves as coming from us to you. See you not that I too have proved it, if this amounts to proof? And yet I would have you learn what is really meant by proof. For indeed I do not even seek for evidence from without to enable me to prove you vipers. For be well assured that this very fact marks in you the nature of vipers, that you have not in your mouth the foundation of truth, but the poison of slanderous abuse, as it is written, "The poison of asps is under their lips." And because this might be said indiscriminately by any one against any one, as though it were asked, Under whose lips? he immediately adds, "Their mouth is full of cursing and bitterness." When, therefore, you say such things as this against men dispersed throughout the whole world, of whom you know nothing whatsoever, and many of whom have never heard the name either of Cæcilianus or of Donatus, and when you do not hear them answering amid silence, Nothing of what you say has reference to us; we never saw it; we never did it; we are totally at a loss to understand what you are saying,—seeing that you desire nothing else than to say what you are entirely powerless to prove, how can you help allowing that your mouth is full of cursing and bitterness? See, therefore, whether you can possibly show that you are not vipers, unless you show that all Christians throughout all nations of the world are traditors, and murderers, and anything but Christians. Nay, in very truth, even though you should be able to know and set before us the lives and deeds of every individual man throughout the world, yet before you can do that, seeing that you act as you do without any consideration, your mouth is that of a viper, your mouth is full of cursing and bitterness. Show to us now, if you can, what prophet, what wise man, what scribe we have slain, or crucified, or scourged in our synagogues. Look how much labor you have expended without in any way being able to prove that Donatus and Marculus were prophets, or wise men, or scribes, because, in fact, they were nothing of the sort. But even if you could prove as much as this, what progress would you have made towards proving that they had been killed by us, when even we ourselves did not so much as know them? and how much less the whole world, whom you calumniate with poisonous mouth? Or whence will you be able to prove that we have a spirit like that of those who murdered them, when you actually cannot show that they were murdered by any one at all? Look carefully to all these points, see whether you can prove any single one of them either about the whole world, or to the satisfaction of the whole world,—in your persevering calumnies against which you show that the charges are true in you, which you falsely propagate against the world.

Nicene and Post-Nicene Fathers: Series I/Volume IV/Donatist Controversy/Answer to the Letters of Petilian, the Donatist/Book II/Chapter 14