Who knows a fool, must know his brother; for one will recommend another.

Related:

• He knows not how to know who knows not also how to unknow.
  Sir Richard...
• One must be poor to know the luxury of giving. --
  George...
• Wealth is not his that has it, but his that enjoys it.
  Poor...
• Learn of the skillful: he that teaches himself hath a fool for a master.
  Poor...
• Bart: He's planning something evil, I know it. It must have something to do with the town's water supply.
  Milhouse: Maybe he's gonna pee in the river! Bart...
• He who knows not and knows that he knows not is ignorant.
  Teach him. He who knows not and knows not that he knows...
• He who knows how to be poor knows everything. --
  Jules Michelet (1798...