2 Peter 2:20-22

20 For if, after they have escaped the defilements of the world by the knowledge of the Lord and Savior Jesus Christ, they are again entangled in them and are overcome, the last state has become worse for them than the first. 21 For it would be better for them not to have known the way of righteousness, than having known it, to turn away from the holy commandment handed on to them. 22 It has happened to them according to the true proverb, “A DOG RETURNS TO ITS OWN VOMIT,” and, “A sow, after washing, returns to wallowing in the mire.”

In this group of verses Peter is piggy backing off of the last part of verse 19, where he states, “for by what a man is overcome, by this he is enslaved.” Peter is speaking of the false teachers who were slaves of corruption; yet in these verses he is giving us a teaching for anyone who is a slave of corruption.

Then he brings a teaching that seems to refer to those spoken of in verse 18, “who barely escape from the ones who live in error.” Yet again the teaching here is for anyone who has escaped some sins by learning of the true gospel of the Lord, and then, if they are overcome by these sins again, they will find themselves more a slave of corruption then they were the first time.

This teaching seems to be identical to what we find in Luke 11:24-26; but here Jesus speaks of unclean spirits that are contributing to the persons sins and corruption.  Hence, I would say that since Satan is always involved in some way with our sins, we may believe that Jesus’ teaching here can also be applied to this 2 Peter passage.

Peter’s teaching that the “last state” becomes worse than the first (v. 20) is devastating. It tells us that if a person escapes from their sins through a knowledge of the Lord, and then later returns to them, they become more entangled in their corruption and also more demonized. This happens because when a man (or a woman) learns about God’s grace and goodness and then rejects it, there will automatically be built up a wall against God—or we could say that Satan builds up a stronghold against them (with more demons), making it harder to receive Him. And that is why Peter declares that it would be better not to have known the way of righteousness.

Then verse 22 gives us the devastating result: he becomes in his sin like a dog eating his own vomit and like a sow wallowing in the mud. He chooses this kind of life rather than a life of grace and glory with God and His Son.