The four debts owed by men.

King Pandu explains the four debts that all are born with.

They are the debts due unto Gods, Rishis ,anscestors and other men  .

The gods are gratified by sacrifices [homam]

The Rishis by study, meditation and ascetism.
The deceased anscestors by begetting children and offering funeral cake.
Other men by leading a humane and inoffensive life.


From Adi parva of Mahabharat section --CXX