12 Petilianus said: "This being the case, brethren, what perversity must it be, that he who is guilty through his own sins should make another free from guilt, when 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.'"
13. Augustine answered: No man, even though he be not guilty through his own sins, can make his neighbor free from sin, because he is not God. Otherwise, if we were to expect that out of the innocence of the baptizer should be produced the innocence of the baptized, then each will be the more innocent in proportion as he may have found a more innocent person by whom to be baptized; and will himself be the less innocent in proportion as he by whom he is baptized is less innocent. And if the man who baptizes happens to entertain hatred against another man, this will also be imputed to him who is baptized. Why, therefore, does the wretched man hasten to be baptized—that his own sins may be forgiven him, or that those of others may be reckoned against him? Is he like a merchant ship, to discharge one burden, and to take on him another? But by the good tree and its good fruit, and the corrupt tree and its evil fruit, we are wont to understand men and their works, as is consequently shown in those other words which you also quoted: "A good man, out of the good treasure of his heart, brings forth good things: and an evil man, out of the evil treasure, brings forth evil things." But when a man preaches the word of God, or administers the sacraments of God, he does not, if he is a bad man, preach or minister out of his own treasure; but he will be counted among those of whom it is said, "Whatsoever they bid you observe, that observe and do; but do not ye after their works:" for they bid you observe what is God's, but their works are their own. For if it is as you say, that is, if the fruit of those who baptize consist in the baptized persons themselves, you declare a great woe against Africa, if a young Optatus has sprung up for every one that Optatus baptized.
Source: Answer to Letters of Petilian, Bishop of Cirta (New Advent)