29 Petilianus said: Over and over again He reproaches the false speakers and liars in such terms as these: ‘You are the children of the devil, for he also was a slanderer from the beginning, and abode not in the truth.'"
30. Augustine answered: We are not wont to say, "He was a slanderer," but "He was a murderer." But we ask how it was that the devil was a murderer from the beginning; and we find that he slew the first man, not by drawing a sword, nor by applying to him any bodily violence, but by persuading him to sin, and thus driving him from the happiness of Paradise. What, then, was Paradise is now represented by the Church. Therefore those are the sons of the devil who slay men by withdrawing them from the Church. But as by the words of God we know what was the situation of Paradise, so now by the words of Christ we have learned where the Church is to be found: "Throughout all nations," He says, "beginning at Jerusalem." Whosoever, therefore, separates a man from that complete whole to place him in any single part, is proved to be a son of the devil and a murderer. But see, further, what is the application of the expression which you yourself employed in saying of the devil, "He was a slanderer, and abode not in the truth." For you bring an accusation against the whole world on account of the sins of others, though even those others themselves you were more able to accuse than to convict; and you abode not in the truth of Christ. For He says that the Church is "throughout all nations, beginning at Jerusalem;" but you say that it is in the party of Donatus.
Source: Answer to Letters of Petilian, Bishop of Cirta (New Advent)