2 Peter 2:22

But it is happened unto them, according to the true proverb,
&c.] Which is true, both in fact and in the application of it, and which lies in the Scriptures of truth, at least the first part of it, ( Proverbs 26:11 ) .

The dog [is] turned to his own vomit again, and the sow that was
washed to her wallowing in the mire;
which expresses the filthy nature of sin, signified by vomit, mire, and dirt, than which nothing is more abominable and defiling; and also the just characters of these apostates, who are filly compared to dogs and swine and likewise their irreclaimable and irrecoverable state and condition, it being impossible they should be otherwise, unless their natures were changed and altered. In the Hebrew language, a "sow" is called (ryzx) , from the root (rzx) , which signifies to "return", because that creature, as soon as it is out of the mire and dirt, and is washed from its filthiness, naturally returns to it again: so such apostates return to what they were before, to their former principles and practices: in this manner the Jews explain the proverb,

``Tobiah returns to Tobiah, as it is said, ( Proverbs 26:11 ) ; as a dog returneth to his vomit ^F18.''