Do as you would be done by, it is a Better Rule in the Doctrine than in the Practice: For Trust as you would be Trusted, will not hold betwixt a Knave and an Honest Man. There's no Dealing with a Sharper but at his Own Play.
Source: L'Estrange 260.
Here is an illustration for the story (image source), showing a dove in her nest.
M0516 (not in Perry)