10 Again, when he hears, "He that is washed by one dead, his washing profits him nought," he will answer, "Christ, being raised from the dead, dies no more; death has no more dominion over Him:" of whom it is said, "The same is He which baptizes with the Holy Ghost." But they are baptized by the dead, who are baptized in the temples of idols. For even they themselves do not suppose that they receive the sanctification which they look for from their priests, but from their gods; and since these were men, and are dead in such sort as to be now neither upon earth nor in the rest of heaven, they are truly baptized by the dead: and the same answer will hold good if there be any other way in which these words of holy Scripture may be examined, and profitably discussed and understood.
For if in this place I understand a baptizer who is a sinner, the same absurdity will follow, that whosoever has been baptized by an ungodly man, even though his ungodliness be undiscovered, is yet washed in vain, as though baptized by one dead. For he does not say, He that is baptized by one manifestly dead, but absolutely, "by one dead." And if they consider any man to be dead whom they know to be a sinner, but any one in their communion to be alive, even though he manages most adroitly to conceal a life of wickedness, in the first place with accursed pride they claim more for themselves than they ascribe to God, that when a sinner is unveiled to them he should be called dead, but when he is known by God he is held to be alive.
In the next place, if that sinner is to be called dead who is known to be such by men, what answer will they make about Optatus, whom they were afraid to condemn though they had long known his wickedness? Why are those who were baptized by him not said to have been baptized by one dead? Did he live because the Count was his faith? — an elegant and well-turned saying of some early colleagues of their own, which they themselves are wont to quote with pride, not understanding that at the death of the haughty Goliath it was his own sword by which his head was cut off.
Source: Answer to Letters of Petilian, Bishop of Cirta (New Advent)