Theophylact of Ohrid

They must be rebuked sharply, so that their "mouths" are stopped. But what is the benefit, when they are of those who do not submit to the truth? For them there is none, but it is beneficial for those whom they might corrupt if the bishop remains silent; for their corruption the bishop himself will give an account. Therefore the mouths of such people must be "stopped": if you cannot do this, do not be a bishop. You see what disobedience combined with love of money and "shameful gain" means, how "they subvert whole houses"! …

Commentary on Titus ↗

Augustine of Hippo

But could I do otherwise than utter my feelings when my heart was pierced with such grief? Shall they do such things, and am I to be commanded to hold my peace? When He commands me by the mouth of the apostle saying that those who teach what they ought not must be rebuked by the bishop, shall I be silent through dread of their displeasure? …

Letters 34.4, 35.3 ↗

Thomas Aquinas

Then when he says, who subvert whole houses, he shows their zeal: first, from the harm they inflict; second, from the false doctrine they teach; third, from the gain they desire. The harm they cause is that they subvert whole houses. For Catholic doctrine is preached openly in the Church, but heretics teach in secret. That is why they seek hidden places: stolen water is sweet, and bread eaten in secret is pleasant (Prov 9:17). …

Commentary on Titus ↗