Albert Barnes Commentary Jude 1:10

"But these rail at whatsoever things they know not: and what they understand naturally, like the creatures without reason, in these things are they destroyed." — Jude 1:10 (ASV)

But these speak evil of those things which they know not. These false and corrupt teachers use reproachful language about those things that are entirely beyond their understanding.

But what they know naturally. As mere human beings, as animals; that is, in things pertaining to their physical nature, or in which they are on a level with the brute creation. The reference is to the natural instincts, the impulses of appetite, and passion, and sensual pleasure.

The apostle's idea seems to be that their knowledge was confined to these things. They did not rise above them to the intelligent contemplation of those higher things, about which they used only reproachful language.

There are many such people in the world. Towards high and holy things, they use only reproachful language. They do not understand them, but they can rail at them. Their knowledge is limited to matters of sensual indulgence, and all their intelligence in this regard is used only to corrupt and destroy themselves.

As brute beasts. Animals without intelligence.

In those things they corrupt themselves. They live only for sensual indulgence and sink deeper and deeper into sensual gratifications.