For if, after they have escaped the defilements of the world through the knowledge of our Lord and Savior Jesus Christ, they are again entangled in them and overcome, the last state has become worse for them than the first. For it would have been better for them never to have known the way of righteousness than after knowing it to turn back from the holy commandment delivered to them. What the true proverb says has happened to them: "The dog returns to its own vomit, and the sow, after washing herself, returns to wallow in the mire."
2 Peter 2:20-22
This is a very difficult passage from several points of view. It is not certain whether the reference is to the false teachers themselves or to those whom they deceive and lead astray, and it is even less certain whether we are to take from this that true Christians can really fall away from grace or whether this final falling away indicates that they were not ever in a state of grace. One suggestion is that we find a key to the meaning in Christ's words in Matthew 12:45. Our Lord's parable there about the unclean spirit going out of a man and returning subsequently with seven others more wicked than himself contains almost the same words that we have here - 'their last state is worse than the first'. If this be so, then Peter's reference is to those who have not truly received newness of life through Christ, for in Christ's parable although the evil spirit goes out there is no mention of the good Spirit coming in, and where He is not, there can be no real spiritual life. It is sadly true in experience that those who seem to be truly converted but prove to have been only stirred emotionally by the Word do relapse into a state worse than before and become almost impervious to any further spiritual influence. This is very frightening, and seems accentuated by the grim words in Hebrews 6:4-8 and we should be all the more concerned to make our calling and election sure in face of such warnings. This we may do by attending to Peter's earlier exhortations (see 1:5-8). As Jesus said 'he that endureth to the end shall be saved'.