At thy right hand there are pleasures for evermore (Ps. 16: 11)
“As a dog returneth to his vomit, so a fool returneth to his folly” (Proverbs 26:11).
Presumably the dog vomited the way it did for some reason. Whatever he had eaten did not agree with him, as was indicated by the vomiting. But the dog does not think things through, being a dog, and simply returns to what he just got rid of.
The dog has some excuse, again, being a dog, but the fool is in a different position. Being a man, he should be in a position to think it through—and yet he refuses to do so. This is yet another reminder that in Scripture being a fool is not an IQ issue, but is rather a moral issue. The fool does something really foolish, and the whole thing blows up. Rather than take the lesson from the affair, he reasons that he needs “more of the hair of the dog that bit him.” For some reason, he feels the need to do it again.
As it happens, this is a proverb that is quoted by the apostle Peter. “But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire” (2 Peter 2:22). Peter is dissecting the impudence and folly of certain false teachers. They were delivered from the world’s external corruptions by their initial profession of faith, but then they started to dabble in things that were best left alone. Those things included vanity, a promise of liberty, and “permitted” wantonness. From this it appears that they were abusing grace, being antinomians of some stripe.
Another proverb is quoted alongside this one, which is that when you hose down a pig, what you have is a wet pig. You can wash the mire off, but you can’t wash the pig off. And as a result of that, the pig returns to its wallowing in the mire. In short, this is a vivid picture of people who have attached themselves to the faith externally, but without the change of heart and nature that is brought in by the new birth.