Charles Ellicott Commentary 2 Peter 2:22

"It has happened unto them according to the true proverb, The dog turning to his own vomit again, and the sow that had washed to wallowing in the mire." — 2 Peter 2:22 (ASV)

But it is happened unto them according to the true proverb.—More literally, There has happened to them what the true proverb says; “but” is of very doubtful authority. The word for “proverb” is the one used elsewhere only by St. John in his Gospel, and there translated once “parable” and three times “proverb.” “Parable,” or “allegory,” would have been best in all four cases (John 10:6 (see Note); John 16:25; John 16:29).

The first proverb is found in Proverbs 26:11. If that is the source of the quotation, we have here an independent translation of the Hebrew, for the LXX. gives an entirely different rendering, “dog” being the only word in common to the two Greek versions. The word for “vomit” here is possibly formed by the writer himself; that for “wallowing” is also a rare word. The LXX. adds, “and becomes abominable,” which has no equivalent in the existing Hebrew text; and it has been suggested that these words may misrepresent the Hebrew original of the second proverb here.

But it is quite possible that both proverbs come from popular tradition and not from Scripture at all. If, however, the Book of Proverbs is the source of the quotation, it is worth noting that St. Peter recalls passages from Proverbs no less than four times in as many chapters in his First Epistle (1 Peter 1:7; 1 Peter 2:17; 1 Peter 4:8; 1 Peter 4:18). In the Greek, neither proverb has a verb, as is so often the case in such sayings—a dog that has returned to his own vomit; a washed sow to wallowing in the mire; just as we say, “the dog in the manger,” or “a fool and his money.”

The word for “mire,” not a very common one, is used by Irenaeus of the Gnostic false teachers of his day, who taught that their fine spiritual natures could no more be hurt by sensuality than gold by mire. “For in the same way as gold when plunged in mire does not lay aside its beauty, but preserves its own nature, the mire having no power to injure the gold, so they say that they, no matter what kind of material actions they may be involved in, cannot suffer any harm, nor lose their spiritual essence” (Chapter 6, section 2). But it is not probable that Irenaeus knew this Epistle.