'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, 
realizing 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 dick.'