Vita S. Antoni (Life of St. Anthony)

⁶⁸ And he was altogether wonderful in faith and religious, for he never held communion with the Meletian schismatics, knowing their wickedness and apostacy from the beginning; nor had he friendly dealings with the Manichæans or any other heretics; or, if he had, only as far as advice that they should change to piety. For he thought and asserted that intercourse with these was harmful and destructive to the soul. In the same manner also he loathed the heresy of the Arians, and exhorted all neither to approach them nor to hold their erroneous belief. And once when certain Arian madmen came to him, when he had questioned them and learned their impiety, he drove them from the mountain, saying that their words were worse than the poison of serpents.