a dog

Exodus 8:15
When Pharaoh saw there was relief, however, he hardened his heart and would not listen to Moses and Aaron, just as the LORD had said.

Matthew 12:45
Then it goes and brings with it seven other spirits more evil than itself, and they go in and dwell there; and the final plight of that man is worse than the first. So will it be with this wicked generation."

2 Peter 2:22
Of them the proverbs are true: "A dog returns to its vomit, " and, "A sow that is washed goes back to her wallowing in the mud."

returneth to his folly