Jude 1:13

Raging waves of the sea - Compare 2 Peter 2:18. They are like the wild and restless waves of the ocean. The image here seems to be, that they were noisy and bold in their professions, and were as wild and ungovernable in their passions as the billows of the sea.

Foaming out their own shame - The waves are lashed into foam, and break and dash on the shore. They seem to produce nothing but foam, and to proclaim their own shame, that after all their wild roaring and agitation they should effect no more. So with these noisy and vaunting teachers. What they impart is as unsubstantial and valueless as the foam of the ocean waves, and the result is in fact a proclamation of their own shame. Men with so loud professions should produce much more.

Wandering stars - The word rendered “wandering” (πλανῆται planētai) is that from which we have derived the word “planet.” It properly means one who wanders about; a wanderer; and was given by the ancients to planets because they seemed to wander about the heavens, now forward and now backward among the ether stars, without any fixed law. - Pliny, Nat. Hist. ii. 6. Cicero, however, who saw that they were governed by certain established laws, says that the name seemed to be given to them without reason. - De Nat. Deo. ii. 20. So far as the “words” used are concerned, the reference may be either to the planets, properly so called, or to comets, or to “ignes fatui,” or meteors. The proper idea is that of stars that have no regular motions, or that do not move in fixed and regular orbits. The laws of the planetary motions were not then understood, and their movements seemed to be irregular and capricious; and hence, if the reference is to them, they might be regarded as not an unapt illustration of these teachers. The sense seems to be, that the aid which we derive from the stars, as in navigation, is in the fact that they are regular in their places and movements, and thus the mariner can determine his position. If they had no regular places and movements, they would be useless to the seaman. So with false religious teachers. No dependence can be placed on them. It is not uncommon to compare a religious teacher to a star, Revelation 1:16; Revelation 2:1. Compare Revelation 22:16.

To whom is reserved the blackness of darkness for ever - Not to the stars, but to the teachers. The language here is the same as in 2 Peter 2:17. See the notes at that verse.