Fate!
Throughout the entire book, most of the characters use language that summon the devil. Inevitably, the characters who anger the devil end up with terrible misfortune. They are careless in their speech, but often the deliberately ignore a warning from Woland or his followers. It becomes clear that Woland punishes people for being greedy or dishonest.
In Chapter 17, the importance of the word "devil" as a swear is very clear. Prokhor Petrovich yells at Behemoth, "The devil take me!" Soon after, his body disappears. He is left as an independently operating suit. The reader also knows that Petrovich had been warned many times by his secretary to stop using "devil" as a swear word. Eventually Petrovich's ignorance istaken care of by the devil himself.
