A baker in the village bought butter from a nearby farmer.

One day he weighed the amount of butter he had purchased and found that the farmer had reduced the amount of butter he sold, but charged him the full price. So the baker accused the farmer of fraud. In court, the judge asked the farmer,

“Do you have a verified scale and weights?”

“I do not,” the farmer replied. “Then how do you measure the amount of butter you sell?” asked the judge.

The farmer replied,

“When the baker started buying my butter, I realized that I should also buy his bread. I started using his half-kilogram bread as a weight on my scale when I weighed the butter. If the weight of my butter is less, then the baker is to blame.”

"For you will be treated as you treat others. The standard you use in judging is the standard by which you will be judged." 

Matthew 7,2