The most obvious motif in this story is greed. Tom's greed leads him to throw away his eternal comfort for his immediate desire for material wealth and power. He is so greedy, in fact, that he will not take unending wealth if it means he'll have to share it with his wife. Irving's message is clear: greed has no positive consequences. In the end, Tom is taken, and all he built - all those material possessions - simply disappear.
However, there is also the motif of hypocritical behavior. Tom is more than willing to sign away his soul when he wants something, but he doesn't have the integrity to uphold his promise. Tom spends his life eschewing religion, but spends the last years of his life acting the part of a devout Christian - "Tom's zeal became as notorious as his riches" - just for his own gain.