2 Peter 2:22

They verify the truth of the proverb: "The dog turns back to what he has vomited, the sow when washed will wallow in the mire."

Matthew 12:45

Then it goes off to fetch seven other spirits worse than itself; they go in and dwell there, and the last state of that man is worse than the first. This is how it will be with the present evil generation."

Treasury of Scripture Knowledge

Summary

As a dog returneth to his vomit, so a fool returneth to his folly.

Bible References

A dog

Matthew 12:45
Then it goes off to fetch seven other spirits worse than itself; they go in and dwell there, and the last state of that man is worse than the first. This is how it will be with the present evil generation."
2 Peter 2:22
They verify the truth of the proverb: "The dog turns back to what he has vomited, the sow when washed will wallow in the mire."