What is the ruling on the money this brother received from "Social Services" over four months? Must it be returned to the government, considering he knew it was stipulated that he inform them of any income and he did not, and taking into account that he does not possess the full amount and that informing them may lead to legal problems?

Taking the money of disbelievers through treachery and betrayal is forbidden, because treachery is forbidden in Islam, whether with a Muslim or a disbeliever. It is obligatory to respect the contract with those countries. It was obligatory upon the brother to confess his action, regardless of his religion, which he concealed from them. Among the conditions for repentance from taking people's money unjustly is to return the rights to their owner, even if he is a disbeliever. If there is fear of scandal, it is permissible to return the right in a way that preserves his dignity, such as sending the amount by mail or entrusting someone without mentioning his name. Whoever does not possess the full amount should return what he has now, and the remainder remains a debt upon him, to be returned whenever he is able.