When the fox preaches, beware of your geese.

A person who appears to offer moral advice may be pursuing the very interest that would harm those listening. Fine language and virtuous poses should not automatically be taken as proof of goodwill.

The saying urges caution when someone’s counsel conveniently gives them power over what they desire. Applied to a person, its animal imagery makes it a pointed accusation of bad faith, not a neutral description of disagreement.

Use it to warn that a seemingly benevolent adviser may have a self-serving or predatory interest in the outcome, especially when those urged to trust them would be exposed to loss. Because it implies bad faith, use it cautiously when speaking about a person.