Jude 1:16

These people have no confidence in their own teaching. For how can it not be dangerous to spread it with such wickedness and blasphemy?

These are murmurers, grumblers, etc. The more anyone murmurs and grumbles about the present labors of the Church, the less they have extinguished the desires of the flesh within themselves. But on the contrary, holy Daniel and other men of heavenly desires, as diligently as they only desire the things above, so much more scornfully do they despise all passing things that seem adverse.

These are grumblers, complainers, walking according to their own lusts; and their mouth speaks great swelling words, flattering people to gain advantage. After this, however, having been freed from the accommodation of these ungodly ones, Jude now also addresses the matter itself, accusing their vices, calling them grumblers and complainers. There is indeed a grumbler, one who, under his breath and without speaking out, complains to the one who is displeased. The complainer, on the other hand, always and constantly engages in contempt. These wretched ones are murmurers and complainers, Jude says. For they do not have the boldness to engage in their teaching through shameful means. For it is not without danger to publicly proclaim recklessness with wickedness and blasphemy. And they are complainers, slandering both other people and the truth, in order to set up their own evils and obscenity as if they were something good. As he has said concerning Balaam, that they have poured themselves out for profit just like him, he now states more clearly that they flattering people to gain advantage, admiring indeed, by flattering those in authority, but the profit is actually the gain.