Noblesse Oblige

The Dictionnaire de l’Académie française defines it thus:
Whoever claims to be noble must conduct himself nobly.
(Figuratively) One must act in a fashion that conforms to one's position, and with the reputation that one has earned.
The Oxford English Dictionary says that the term "suggests noble ancestry constrains to honorable behavior; privilege entails to responsibility". Being a noble meant that one had responsibilities to lead, manage and so on. One was not to simply spend one's time in idle pursuits.

(source: Wikipedia)