The protagonist in "The Devil and Tom Walker" by Washington Irving is Tom Walker, a very poor, miserable farmer. One day he is walking home and meets a man in the forest. Tom asks the man who he is; among other things, the man claims he is "the great patron and prompter of slave dealers, and the grand master of the Salem witches." Tom understands that the man who stands before him is the devil, Satan, Old Scratch, or whatever other names people have for him.
After Tom loses his wife (and gains some peace), he finds the devil again, and they begin to bargain over the pirate's treasure which Tom found but which the devil claims is his.
[T]hey 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 favours; 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. He proposed, therefore, that Tom should employ it in the black traffick; that is to say, that he should fit out a slave ship. This, however, Tom resolutely refused; he was bad enough in all conscience; but the devil himself could not tempt him to turn slave dealer.
The devil insists that the money must be spent "in his service," and his first choice is that Tome use the money to begin trafficking in slaves. (We should not be surprised, as that is one of the titles the devil claimed for himself when he introduced himself to Tom in the beginning.)
This is the one thing, apparently, that Tom Walker will not do: he will not become a slave trader. He is, however, perfectly will to accept the devil's second suggestion, and he becomes a usurer, one who loans money for exorbitant profit. In accepting the deal, of course, he loses his soul.