“But it has happened to them according to the true proverb: ‘a dog returns to his own vomit,’ and, ‘a sow, having washed, to her wallowing in the mire’ (2 Peter 2:22).
While dogs in the New Testament era were occasionally kept as pets, they were frequently regarded as scavengers and pests. Because of this, people often used the word “dog” in a derogatory manner to describe an offensive individual. Those characteristics thus served as fitting analogies for the false teachers of 2 Peter chapter two. That comparison draws upon the imagery of Proverbs 26:11, where this same word-picture is used to depict the actions of a foolish individual.
Our second illustration (which portrays a pig returning to the mud), is an extra-Biblical adage. Pigs were unclean animals according to the Old Testament law, and that made them ideal stand-ins for these heretical teachers as well. However, there may be more to these analogies than meets the eye.
For instance, a dog returns to the internal impurities it has expelled from inside. A pig returns to the external impurities it finds outside. In our first example, these internal impurities emerge from within, and are comparable to those who are internally enslaved to corruption (2 Peter 2:19). Our second example highlights the external impurities associated with those who “who walk according to the flesh in the lust of uncleanness” (2 Peter 2:10).
So, the external behaviors of these animals reflect their internal natures, just as the corrupt behaviors of these false teachers reflect their immoral character. That leads us to an important takeaway from this chapter…
“There is no suggestion in the proverb that they had experienced any change in their natures. They were unclean before they were delivered from the vomit and the mud, and they were still unclean when they returned to them. So it is with the people of whom Peter wrote. They had undergone a moral reformation but they had never received a new nature…
This passage should not be used to teach that true believers may fall from grace and be lost. These people never were true believers. They never received a new nature. They demonstrated by their last state that their nature was still unclean and evil. The lesson is, of course, that reformation alone is not only insufficient, but is positively dangerous, because it can lull a person into a false security. Man can receive a new nature only by being born again. He is born again through repentance toward God and faith in our Lord Jesus Christ.” (1)
(1) William Macdonald, Believer’s Bible Commentary. Edited by Arthur Farstad, Thomas Nelson Publishers [2 Peter 2:1-22]