Chapter 17.
38 Petilianus said: "Thus, thus, you wicked persecutor, under whatsoever cloak of righteousness you have concealed yourself, under whatsoever name of peace you wage war with kisses, under whatsoever title of unity you endeavor to ensnare the race of men — you, who up to this time are cheating and deceiving, you are the true son of the devil, showing your parentage by your character."
39. Augustine answered: Consider in reply that these things have been said by us against you; and that you may know to which of us they are more appropriate, call to mind what I have said before.
Source: Answer to Letters of Petilian, Bishop of Cirta (New Advent)