What is the “Change”?

Tom's change begin as he ages, "having secured the good things of this world, he began to feel anxious about the next." As a result, he attempts to make plans to "cheat" the devil. Tom begins to attend church regularly, he prays "loudly and strenuously," and he passes judgment on his fellow churchgoers. He starts carrying his Bible around at all times, and he even places a large Bible on his desk for the benefit of his business associates. Later, he had his horse shod and buried with its feet sticking up (he believed that the end of the world would turn everything upside down), so the horse would be prepared for a quick escape from Old Scratch's wrath.