{Whose mouths must be stopped} (hous dei epistomizein).
Literally, "whom it is necessary to silence by stopping the
mouth." Present active infinitive epistomizein, old and common
verb (epi, stoma, mouth), here only in N.T. To stop the mouth
either with bridle or muzzle or gag. {Overthrow}
(anatrepousin). Old and common verb, to turn up, to overturn.
In N.T. only here and  2Ti 2:18 . In papyri to upset a family by
perversion of one member. {Things which they ought not} (ha m(880a)dei). Note subjective negative m(885c) with indefinite relative and
indicative mode. {For filthy lucre's sake} (aischrou kerdous
charin). The Cretans are given a bad reputation for itinerating
prophets for profit by Polybius, Livy, Plutarch. Paul's warnings
in  1Ti 3:3,8  6:5  reveal it as "a besetting temptation of the
professional teacher" (Parry). See verse  7  above. Disgraceful
gain, made in shameful ways.