The Devil and Tom Walker

From the text:

By degrees, however, Tom brought him to business, and they began to haggle about the terms on which the former was to have the pirate’s treasure. There was one condition which need not be mentioned, being generally understood in all cases where the devil grants favors; but there were others about which, though of less importance, he was inflexibly obstinate. He insisted that the money found through his means should be employed in his service.

The one condition that need not be mentioned is Tom's soul.... he's given it to the Devil.