The Tool of Discouragement
There is an old legend about Satan one day having a yard sale. He thought he'd get rid of some of his old tools that were cluttering up the place. So there was gossip, slander, adultery, lying, greed, power-hunger, and more laid out on the tables. Interested buyers were crowding the tables, curious, handling the goods. One customer, however, strolled way back in the garage and found on a shelf a well-oiled and cared-for tool. He brought it out to Satan and inquired if it was for sale. "Oh, no!" Satan answered. "That's my tool. Without it I couldn't wreck the church! It's my secret weapon!" "But what is it?" the customer inquired.
"It's the tool of discouragement," the devil said.
In the text Jesus is talking to the church about their attitude and deportment toward the prophets God sends among us as shepherds. He speaks frankly about acceptance and rejection, about kindness and trust. In short, he promises that in the minister's success among us shall come our own reward. (Matt 10:40-41)
Source: Stephen M. Crotts and Stan Purdum, Sermons For Sundays: After Pentecost (First Third): “Hidden In Plain View,” CSS Publishing Company, Inc.; in an email sent by eSermons.com.