Proverbs 26:11

As a dog hath returned to its vomit, A fool is repeating his folly.

2 Peter 2:22

and happened to them hath that of the true similitude; 'A dog did turn back upon his own vomit,' and, 'A sow having bathed herself -- to rolling in mire.'

Exodus 8:15

And Pharaoh seeth that there hath been a respite, and he hath hardened his heart, and hath not hearkened unto them, as Jehovah hath spoken.

Matthew 12:45

then doth it go, and take with itself seven other spirits more evil than itself, and having gone in they dwell there, and the last of that man doth become worse than the first; so shall it be also to this evil generation.'

Treasury of Scripture Knowledge

Summary

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

General references

Bible References

A dog

Exodus 8:15
And Pharaoh seeth that there hath been a respite, and he hath hardened his heart, and hath not hearkened unto them, as Jehovah hath spoken.
Matthew 12:45
then doth it go, and take with itself seven other spirits more evil than itself, and having gone in they dwell there, and the last of that man doth become worse than the first; so shall it be also to this evil generation.'
2 Peter 2:22
and happened to them hath that of the true similitude; 'A dog did turn back upon his own vomit,' and, 'A sow having bathed herself -- to rolling in mire.'

General references

Isaiah 28:8
For all tables have been full of vomit, Filth -- without place!
Jeremiah 34:11
and they turn afterwards, and cause the men-servants and the maid-servants to return, whom they had sent forth free, and they subdue them for men-servants and for maid-servants.