John Gill, on Titus 1:11

Whose mouths must be stopped,.... Or they be silenced, by reasons and arguments fetched out of the word of God; as were the Sadducees and Pharisees by Christ, so that they durst ask him no more questions; and as the Jews at Damascus were by Saul, who confounded them, proving in the clearest and strongest manner, that Jesus was the very Christ: who subvert whole houses; into which they creep; that is, whole families, whose principles they corrupt, whose faith they overthrow, and carry them away with their own errors; and therefore, since this was the case not of a single person, or of a few, but of whole families, it was high time to attempt to convince them, and stop their mouths, that they might proceed no further: teaching things which they ought not; which were not agreeable to the perfections of God, to the Scriptures of truth, to sound doctrine, and which were hurtful and pernicious to the souls of men: and that only for filthy lucre's sake; having no regard to the glory of God, the honour and interest of Christ, or the good of immortal souls; only seeking to gain popular applause and honour from men, and to gather and increase worldly substance. Covetousness was a sin which the Cretians were remarkably guilty of (l). (l) Cornel. Nepos, l. 23. c. 9.