Proverbs 26:11

Like a dog returning to his vomit [is] a fool reverting to his folly.

2 Peter 2:22

The [statement] of the true proverb has happened to them, "A dog returns to its own vomit," and "A sow, [after] washing herself, [returns] to wallowing in the mud."

Exodus 8:15

And Pharaoh saw that there was relief, and he made his heart {insensitive}, and he did not listen to them, as Yahweh had spoken.

Matthew 12:45

Then it goes and brings along with itself seven other spirits more evil than itself, and [they] go in [and] live there. And the last [state] of that person becomes worse than the first. So it will be for this evil generation also!"

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 saw that there was relief, and he made his heart {insensitive}, and he did not listen to them, as Yahweh had spoken.
Matthew 12:45
Then it goes and brings along with itself seven other spirits more evil than itself, and [they] go in [and] live there. And the last [state] of that person becomes worse than the first. So it will be for this evil generation also!"
2 Peter 2:22
The [statement] of the true proverb has happened to them, "A dog returns to its own vomit," and "A sow, [after] washing herself, [returns] to wallowing in the mud."

General references

Isaiah 28:8
for all [the] tables are full [of] disgusting vomit, {with no place left}.
Jeremiah 34:11
But {afterward} they turned back and they brought back the [male] slaves and the female slaves whom they had let go free, and they subdued them as [male] slaves and female slaves.