John Gill, on Jude 1:16

These are murmurers,.... That is, at others; secretly, inwardly, in a muttering way, grunting out their murmurs like swine; to which, for their filthiness and apostasy, false teachers may be filly compared: and their murmurs might be both against God and men; against God, against the being of God, denying, or at least wishing there was no God, and uneasy because there is one; against the perfections of God, particularly his sovereignty over all, his special goodness to some, his wisdom, justice, truth, and faithfulness; against his purposes and decrees, both with respect to things temporal, spiritual, and eternal; against the providence of God and his government of the world, and the unequal distribution of things in it; and especially against the doctrines of free grace, and the ordinances of the Gospel: and not only are they murmurers against God, and all divine things and persons, but also against men; particularly against civil magistrates, who restrain them, and are a terror to them; and against the ministers of the Gospel, whose gifts and usefulness they envy; and indeed against all men, their neighbours, and what they enjoy, and at everything that goes besides themselves: it follows, complainers; some join the above character and this together, and read, as the Vulgate Latin version, "complaining murmurers"; others, as the Syriac version, place not only a comma, but a copulative between them; and as the former may design secret and inward murmuring, this may intend outward complaining in words; not of their own sins and corruptions, nor of the sins of others, with any concern for the honour of religion; or of the decay of powerful godliness in themselves or others; or of the failure of the Gospel, and the decrease of the interest of Christ; but either of God, that he has not made them equal to others in the good things of life, as the Arabic version renders it, "complaining of their own lots"; or that he lays so much affliction upon them more than on others; or of men, that their salaries are not sufficient, and that they are not enough respected according to their merit; and indeed, as the Syriac version reads, "they complain of everything", and are never satisfied and easy: walking after their own lusts; which are carnal and worldly; see Gill on Pe2 3:3, and their mouth speaketh great swelling words; both against God and men; and this may point at their boast of knowledge, their great ostentation of learning, their vain and empty doctrines, their high flights, their rhetorical style, and bombast language: having men's persons in admiration because of advantage; crying up men of their own stamp for the advantage of the party; and giving flattering titles to men of wealth and riches, for the sake of their money: so the Ethiopic version, "they studied to please persons, to make gain of them"; they were respecters of persons; so the phrase is used by the Septuagint in Deu 10:17, and in Job 22:8, and in Pro 18:5 and in Isa 9:15.