Here's what it makes me think about, from the Gospel according to Matthew:
"When an unclean spirit has gone out of a man, it wanders through dry places, and finds no rest. Then it decides to return to the house from which it came. It goes and takes with it seven other spirits more evil than itself, and they enter and dwell there, and the last state of that man is worse than the first."
Usually understood as Jesus warning against trying to live a godly life through one's own willpower, without seeking help from God. If somebody whose heart has never been renewed by Jesus tries to live according to biblical teachings for the sake of appearances, he may succeed for a time. But sooner or later the old evil nature will end up getting the better of him. I think that dynamic helps to explain some of the truly spectacular moral failings in priests, televangelists, etc. that we've seen over the years.