This was in a chabad.org article for this week’s parsha. Starting the Book of Leviticus.
I have copied it from chabad:
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Whenever we study about the sin-offering—the sacrifice that was brought to atone for the inadvertent committing of a sin—I am reminded of the adorable story of a rabbi who is walking home from synagogue one Friday night, and through an open window he sees three of his prominent congregants playing cards. He knocks on the door, with no answer. Finding the door unlocked, he enters the house where he discovers a heated card game underway, bets and counter-bets being fervently exchanged, money flying back and forth. Despite his entrance, they barely notice him.
“Gentlemen,” he began in a loud but loving voice, “what’s happening here? Surely, you’ve forgotten that it is Shabbat?”
“Quite frankly, rabbi,” one of them responds, “we remembered.” The others nod in agreement.
“Well then,” the rabbi continues, “surely you’ve forgotten that playing cards is not in the spirit of Shabbat, and it is forbidden to handle money on Shabbat?”
“Quite frankly, rabbi, we remembered that as well,” said the self-appointed spokesman.
Perplexed, the rabbi asks, “Well then, is there anything accidental about this situation?”
“Yes rabbi,” he responds, “We’ve forgotten to draw the drapes!”