19. These be they--showing that their characters are such as Peter and Paul had foretold.
      separate themselves--from Church communion in its vital, spiritual reality: for outwardly they took part in Church ordinances (Jude 12). Some oldest manuscripts omit "themselves": then understand it, "separate," cast out members of the Church by excommunication (Isa 65:5; 66:5; Lu 6:22; Joh 9:34; compare "casteth them out of the Church;" 3Jo 10). Many, however, understand "themselves," which indeed is read in some of the oldest manuscripts as English Version has it. Arrogant setting up of themselves, as having greater sanctity and a wisdom and peculiar doctrine, distinct from others, is implied.
      sensual--literally, "animal-souled": as opposed to the spiritual, or "having the Spirit." It is translated, "the natural man," 1Co 2:14. In the threefold division of man's being, body, soul, and spirit, the due state in God's design is, that "the spirit," which is the recipient of the Holy Spirit uniting man to God, should be first, and should rule the soul, which stands intermediate between the body and spirit: but in the animal, or natural man, the spirit is sunk into subserviency to the animal soul, which is earthly in its motives and aims. The "carnal" sink somewhat lower, for in these the flesh, the lowest element and corrupt side of man's bodily nature, reigns paramount.
      having not the Spirit--In the animal and natural man the spirit, his higher part, which ought to be the receiver of the Holy Spirit, is not so; and therefore, his spirit not being in its normal state, he is said not to have the spirit (compare Joh 3:5, 6). In the completion of redemption the parts of redeemed man shall be placed in their due relation: whereas in the ungodly, the soul severed from the spirit shall have for ever animal life without union to God and heaven--a living death.

JFB.