2 Peter 2:21-22

21For it would have been better for them not to have [personally] known the way of righteousness, than to have known it and then to have turned back from the holy commandment [verbally] handed on to them.

22The thing spoken of in the true proverb has happened to them, “The dog returns to his own vomit,” and, “A sow is washed only to wallow [again] in the mire.”