Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Donatist Controversy.: Chapter 25

Chapter 25.—58.  Petilianus said:  "For when you in your guilt perform what is false, I do not celebrate baptism twice, which you have never celebrated once."

59.  Augustin answered:  In the first place, you do not convict us of guilt.  And if a guilty man baptizes with a false baptism, then none of those have true baptism who are baptized by men in your party, that are, I do not say openly, but even secretly guilty.  For if he who gives baptism gives something that is God’s, if he is already guilty in the sight of God, how can he be giving something that is God’s if a guilty man cannot give true baptism?  But in reality you wait till he is guilty in your sight as well, as though what he proposes to confer were something that belonged to you.