A priest goes into a barbershop and gets a haircut. After, he thanks the barber and asks how much he owes him. The barber says, "Father, you're a holy man, a man of the cloth, I couldn't charge you, it's on the house." The priest says, "Thank you very much," and leaves.
The next day, magically appearing on the doorstep of the barbershop are 12 gold coins.
A few days later, a Buddhist monk goes in for a shave and a shine, and when the time comes to pay, the barber says, "No money, please, you're a spiritual leader, a man of the people, it's on the house."
The next day, magically appearing on the doorstep are 12 rubies.
The following week a rabbi comes in, gets a haircut, goes to pay, and the barber says, "No, Rabbi, you are a learned man, a wise man, I can't take any money from you, go in peace."
The next day, magically appearing on the doorstep of the barbershop are 12 rabbis.