"There are those who have heard [Polycarp] tell how when John the disciple of the Lord went to bathe at Ephesus, and saw Cerinthus inside, he rushed out of the bath without washing, but crying out, 'Let us escape, lest the bath should fall while Cerinthus the enemy of the truth is in it.' Polycarp himself, when Marcion once met him and said, 'Do you know us?' answered, 'I know you, the first-born of Satan.' The apostles and their disciples took such great care not even to engage in conversations with the corrupters of the truth, as Paul also said, 'A heretical man [(ἁιρετικὸν ἄνθρωπον)] after a first and second warning avoid, knowing that such a man has fallen away and is a sinner, being self-condemned.'"
Irenaeus, Against heresies 3.3.4, trans. Edward Rochie Hardy (LCC 1, 374). The words of Paul are taken from Titus 3:10-11 (αἱρετικὸν ἄνθρωπον μετὰ μίαν καὶ δευτέραν νουθεσίαν παραιτοῦ,