It is Prohibited to Take this Money
Question :
My father, who is old and blind, owns a very small store. A number of years ago, he and my mother went to the National Welfare Office; a yearly stipend was allotted to them, and my mother officially appointed my father as her agent: he was authorized to receive her share. My father still takes his share and hers annually, she died four years ago; based on the authorization given to him by my mother, he is still able to obtain her share as well. Is my father sinning by doing this?
Answer:
Since your mother's allowance is intended for her benefit, and since she has died, your father has no right to continue to take her allowance. He should inform those in authority of what has happened, and if he has a new wife, he should make a new request for aid under her name; otherwise he has no right to his deceased wife's allowance.
Source:
Ibn Jibreen
Fatawa Islamiyah, Vol. 8 Page 385