incumbent (up)on (someone)
Imposed or expected as an obligation, duty, or requirement on someone. As the wealthier citizens of the country, it's my firm belief that it is incumbent upon us to contribute toward the welfare of those who are less fortunate. He felt it was incumbent on him to take over the responsibilities of his father's business.
incumbent on
Also, incumbent upon. Imposed as an obligation or duty on, obligatory for. For example, He felt it was incumbent on us all to help the homeless. [Mid-1500s]