It is just like English sayings and phrases, there are Japanese sayings and phrases as well. It is called [kotowaza ことわざ].

Today’s kotowaza

飼い犬に手をかまれる　Kai inu ni te wo kamareru

kai inu – a dog you keep

te – hands

Kamareru – being bit

 Bite the hand that feeds you.You got bitten by your pet dog.

Its meaning

A person you are always looking after betrays or harms you.

An example

A manger touch a boy how to play a baseball and the boy became a best player in a team. But he suddenly join a rival team. The manager must be feeling of Kai inu ni te wo kamareta.

arigato