But if one accurately mark his words, he has also tempered his rebuke with commendation. For he spoke these things, as marveling at them, that they had become able, however late, to do what seemed almost an impossibility for them. His rebuke, you see, is rather that of one bringing them over, and working upon them to arouse themselves. For in that he appears amazed, he implies both their former wickedness to be great, and their conversion marvellous and beyond expectation. Thus, what has come to pass, says he, that being children of those men, and brought up so badly, they have repented? Whence has come so great a change? Who has softened down the harshness of their spirit? Who corrected that which was incurable?
And see how straightway from the beginning he alarmed them, by laying first, for a foundation, his words concerning hell. For he spoke not of the usual topics: Who has warned you to flee from wars, from the inroads of the barbarians, from captivities, from famines, from pestilences? but concerning another sort of punishment, never before made manifest to them, he was striking the first preparatory note, saying thus, Who has warned you to flee from the wrath to come?
And full well did he likewise call them, generation of vipers. For that animal too is said to destroy the mother that is in travail with her, and eating through her belly, thus to come forth unto light; which kind of thing these men also did being murderers of fathers, and murderers of mothers, 1 Timothy 1:9 and destroying their instructors with their own hands.
Homilies on Matthew
Homily 11; Matthew 3:7