In "The Devil and Tom Walker," why does Tom decide not to make a pact with the devil after his first offer?

When Tom first meets Old Scratch in the forest, he is skeptical about the creature's identity and authenticity.  However, when he reaches home, he sees the permanent black mark left on his forehead by the devil.  He tells his contrary wife about the devil's offer, and she--true to her selfish nature--urges her husband to barter away his soul for material goods.  Her advice and nonchalance about his soul anger Tom, and so he is determined not to accept the offer.  Irving writes that

"however Tom might have felt disposed to sell himself to the devil, he was determined not to do so to oblige his wife; so he flatly refused out of the mere spirit of contradiction."

Thus, Tom most likely would have never made a deal with the devil because he wanted to spite his wife had she not gone into the forest to make her own deal and been killed.