What is the religious ruling on someone who works in a charitable organization and takes money from it without the knowledge of those in charge to pay off his debts and due to the insufficiency of his salary?

What the person did by taking the association's money is Haram (forbidden) and a betrayal of trust. He must repent to Allah and return the full amount to the association, even if indirectly, such as donating it to them. The fact that the person is in debt or needy does not permit him to betray trust or take the association's money unlawfully.