Washington Irving's "The Devil and Tom Walker" is a text which tells the story of a man who sells his soul to the Devil in order to get himself out of his miserable life. Tom's is a miserly and miserable man. He refuses to spend any money and hoards every penny he can. Similarly, Tom's wife is also a miser. Both of the characters are so cheap and miserly that they steal and hoard from each other. They make each other utterly miserable.
Given the nature of the couple, their hatred of each other helps to make the story more believable. While one may not believe in the materialization of the Devil as a man who walks in the swamps, one can tend to picture a very unhappily married couple.
This couple is so unhappy that each of them consider the proposition the Devil has made. Although the Devil made the proposition to Tom, Tom's wife tries to take the deal. She realizes that she can have even more wealth then her husband by doing so.
Essentially, the greedy nature of the couple propels the story forward. Tom's wife goes to make the pact with the Devil and never returns. Having nothing to fear, Tom makes the pact with the Devil and goes on to lead the life of a usurer (money lender). This leads to Tom's own death when he chides the Devil. Without the pressure put on him by his wife, Tom never would have chosen to take the deal offered by the Devil.