51. said: "But if you say that we give baptism twice over, truly it is rather you who do this, who slay men who have been baptized; and this we do not say because you baptize them, but because you cause each one of them, by the act of slaying him, to be baptized in his own blood. For the baptism of water or of the Spirit is as it were doubled when the blood of the martyr is wrung from him. And so our Saviour also Himself, after being baptized in the first instance by John, declared that He must be baptized again, not this time with water nor with the Spirit, but with the baptism of blood, the cross of suffering, as it is written, ‘Two disciples, the sons of Zebedee, came unto Him, saying, Lord, when thou comest into thy kingdom grant that we may sit, one on Thy right hand, and the other on Thy left hand. But Jesus said unto them, Ye ask a difficult thing: can ye drink of the cup that I drink of, and be baptized with the baptism that I am baptized with? They said unto Him, We are able. And He said unto them, Ye can indeed drink of the cup that I drink of; and with the baptism that I am baptized withal shall ye be baptized,’ and so forth. If these are two baptisms, you commend us by your malice, we must needs confess. For when you kill our bodies, then we do celebrate a second baptism; but it is that we are baptized with our baptism and with blood, like Christ. Blush, blush, ye persecutors. Ye make martyrs like unto Christ, who are sprinkled with the baptism of blood after the water of the genuine baptism."

52. answered: In the first place, we reply without delay that we do not kill you, but you kill yourselves by a true death, when you cut yourselves off from the living root of unity. In the next place, if all who are killed are baptized in their own blood, then all robbers, all unrighteous, impious, accursed men, who are put to death by the sentence of the law, are to be considered martyrs, because they are baptized in their own blood. But if only those are baptized in their own blood who are put to death for righteousness’ sake, since theirs is the kingdom of heaven, you have already seen that the first question is why you suffer, and only afterwards should we ask what you suffer. Why therefore do you puff out your cheeks before you have shown the righteousness of your deeds? Why, does your tongue resound before your character is approved? If you have made a schism, you are impious; if you are impious, you die as one guilty of sacrilege, when you are punished for impiety; if you die as one guilty of sacrilege, how are you baptized in your blood? Or do you say, I have not made a schism? Let us then inquire into this. Why do you make an outcry before you prove your case?

Nicene and Post-Nicene Fathers: Series I/Volume IV/Donatist Controversy/Answer to the Letters of Petilian, the Donatist/Book II/Chapter 23