Yankel comes to shul one morning, and at the end of davening he gets up and makes an announcement:
“Hashem, make me win the lottery, and I promise I will give half of it to tzedaka!”
Then he goes out to buy his lottery ticket, and as could be expected, he doesn’t win.
Thoroughly dejected, Yankel walks into the local church. When the services are completed he stands up and makes a similar announcement:
“Yoshke, make me win the lottery, and I promise I will give half of it to charity!”
He buys his afternoon ticket, and lo and behold, he has the winning numbers!
That evening, as the town is abuzz with the news of their newest millionaire, Yankel is spotted by his rabbi coming to daven ma’ariv at his regular minyan.
“Yankel!” exclaims the rabbi. “You still believe in coming to shul? I would think you’d be in church now!”
“Are you crazy?” says Yankel. “That guy actually believed that I’d give half of my winnings to tzedaka…”