"Satan and Sam Shay", a short story by Robert Arthur.
. . . a man who got tricked into agreeing to three bets with the devil . . .
I am told that sin has somewhat declined since Satan met Sam Shay. I cannot vouch for this, but they say that production has definitely fallen off since that evening when Sam Shay won three wagers from the Devil. And this is the tale of it.
The man won all three bets and in rage the devil cursed him so that all the forces of hell would make sure he never won another bet.
Glaring down from his great height, Satan directed an awful gaze upon Sam Shay.
"This is an ill night's work you have done!" he cried, in a voice that shook with rage, so that the skyscrapers nearby trembled a bit, and the next day's papers carried an item concerning a small earthquake. "Hear me well, Sam Shay! From this moment onward, never shall you win another wager! All the forces of hell will be marshalled to prevent you."
The man tried everything but couldn't win.
"Ten dollars," said he to his acquaintance, "to a dime that Seven doesn't win."
The bookie gave him an odd glance. For Seven was the trailer, forty lengths behind and losing distance steadily. Any mortal eye could see that she couldn't win, and it came to him Sam might be daft.
"Twenty dollars!" said Sam Shay. "To a five-cent piece!"
They were odds not to be resisted, and the bookie nodded.
"Taken!" he agreed, and the words were scarce out of his mouth before Seven put on a burst of speed. She seemed to rise into the air with the very rapidity of her motion. Her legs churned. And she whisked forward so fast her astonished jockey was but an ace from being blown out of the saddle by the very rush of air. Closing the gap in a manner quite unbelievable, she came up to the leaders and, with a scant yard to the finish, shot ahead to win.
When lamenting to a friend the friend suggested they could still beat things out by betting against things people wanted to happen such as betting it would rain during a picnic for people who did not want it to rain.
"Sam," he said, voice hoarse, "you have never heard that there's people willing to pay good money to insure the weather'll be as they want it upon a certain day? Have you never heard of insuring against storms, Sam, and against accidents, sickness, twins and such misfortunes? And insuring isn't really betting. It's but a business—a legitimate money-making business."