Betting rules from Damon Runyon

The race is not always to the swift, nor the battle to the strong; but that's the way to lay your bets.
from a variation on Ecclesiastes 9:11

One of these days in your travels, a guy is going to come up to you and show you a nice brand-new deck of cards on which the seal is not yet broken, and this guy is going to offer to bet you that he can make the Jack of Spades jump out of the deck and squirt cider in your ear. But, son, do not bet this man, for as sure as you are standing there, you are going to end up with an earful of cider.

Trust but verify.

- Damon Runyon

Some of these quotes are used in the musical Guys and Dolls which is based on Runyon's short stories.  Nathan Detroit would have been a good floor trader.