53 Then a little after, as he had said, "This being so, brethren, what perversity must that be, that he who is guilty by reason of his own faults should make another free from guilt, whereas the Lord Jesus Christ says, ‘Every good tree brings forth good fruit, but a corrupt tree brings forth evil fruit: do men gather grapes of thorns?' and again, ‘A good man, out of the good treasure of the heart, brings forth good things: and an evil man, out of the evil treasure, brings forth evil things,'" — by which words Petilianus showed with sufficient clearness, that the man who baptizes is to be looked on as the tree, and he who is baptized as the fruit: to this I had answered, If the good tree is the good baptizer, and his good fruit he whom he has baptized, then any one who has been baptized by a bad man, even if his wickedness be not manifest, cannot by any possibility be good, for he is sprung from an evil tree.
For a good tree is one thing; a tree whose quality is concealed, but yet bad, is another. What else did I wish to be understood by those words, except what I had stated a little above, that the tree and its fruit do not represent him that baptizes and him that is baptized; but that the man ought to be received as signified by the tree, his works and his life by the fruit, which are always good in the good man, and evil in the evil man, lest this absurdity should follow, that a man should be bad when baptized by a bad man, even though his wickedness were concealed, being, as it were, the fruit of a tree whose quality was unknown, but yet bad? To which he has answered nothing whatsoever.
Source: Answer to Letters of Petilian, Bishop of Cirta (New Advent)