Dog returns to vomit; washed sow to mud
Here’s what it means
False teachers return to corruption after outward escape, revealing the pull of unchanged nature.
Why the Bible says it this way
The writer uses a picture to explain one thing by describing it as another.
A helpful detail: Peter uses two degrading animal proverbs to describe deliberate return to pollution. The text must be considered in broader teaching about profession, knowledge, and genuine faith.