22 For perhaps some one of you will say to me, All these things which he said against you he wished to have force for this purpose, that he might take away your character, and through you the character of those with whom you hold communion, that neither they themselves, nor those whom you endeavor to bring over to your communion, may hold you to be of any further importance. But, in deciding whether he has given no answer to the words of your epistle, we must look at them in the light of the passage in which he proposed them for consideration.
Let us then do so: let us look at his writings in the light of that very passage. Passing over, therefore, the passage in which I sought to introduce my subject to the reader, and to ignore those few prefatory words of his, which were rather insulting than revelant to the subject under discussion, I go on to say, "He says, ‘What we look for is the conscience of the giver, to cleanse that of the recipient.' But supposing the conscience of the giver is concealed from view, and perhaps defiled with sin, how will it be able to cleanse the conscience of the recipient, if, as he says, ‘what we look for is the conscience of the giver, to cleanse that of the recipient?'
For if he should say that it makes no matter to the recipient what amount of evil may be concealed from view in the conscience of the giver, perhaps that ignorance may have such a degree of efficacy as this, that a man cannot be defiled by the guilt of the conscience of him from whom he receives baptism, so long as he is unaware of it. Let it then be granted that the guilty conscience of his neighbor cannot defile a man so long as he is unaware of it; but is it therefore clear that it can further cleanse him from his own guilt? Whence then is a man to be cleansed who receives baptism, when the conscience of the giver is polluted without the knowledge of him who is to receive it, especially when he goes on to say, ‘For he who receives faith from the faithless receives not faith but guilt?'"
Source: Answer to Letters of Petilian, Bishop of Cirta (New Advent)