At the end of the tax year, the Tax Office sent an inspector to audit the books of a synagogue. While he was checking the books he turned to the Rabbi and said:
"I notice you buy a lot of candles. What do you do with the candle drippings?"
"Good question", noted the Rabbi. "We save them up and send them back to the candle makers, and every now and then they send us a free box of candles."
"Oh", replied the auditor, somewhat disappointed that his unusual question had a practical answer. But on he went, in his obnoxious way: "What about all these biscuit purchases? What do you do with the crumbs?"
"Ah, yes", replied the Rabbi, realising that the inspector was trying to trap him with an unanswerable question. "We collect them and send them back to the manufacturers, and every now and then they send a free box of holy biscuits."
"I see!" replied the auditor, thinking hard about how he could fluster the know-it-all Rabbi. "Well, Rabbi", he went on, "What do you do with all the leftover foreskins from the circumcisions you perform?"
"Here, too, we do not waste", answered the Rabbi. "What we do is save up all the foreskins and send them to the Tax Office, and about once a year they send us a complete prick."