22 But it has happened to them according to the saying of the true proverb: "A dog returns to his own vomit," and, "A sow, having washed, to her wallowing in the mire."
2 Peter 2:22 Cross References - CAB
Proverbs 26:11
11 As when a dog returns to his own vomit, and becomes abominable, so is a fool who returns in his wickedness to his own sin. (26:11A) There is a shame that brings sin, and there is a shame that is glory and grace.