Is it permissible for a wife to take money from her husband without his knowledge, given that he is extravagant and heavily indebted, for the purpose of saving it to face any emergency that might befall him?

The default rule is that a wife is entrusted with her husband's wealth, and it is not permissible for her to dispose of it without his permission, based on the Prophet's (peace be upon him) saying: "The woman is a guardian in her husband's house and is responsible for her charge," and "A woman should not spend anything from her husband's house except with his permission."

Therefore, if the husband provides for his wife and children in a reasonable manner, she does not have the right to take anything from his money for savings or other purposes without his permission. She must return what she took or seek his forgiveness for it.

The wife should advise her husband and explain to him the prohibition of extravagance and the danger of incurring debt without a valid need. Borrowing is forbidden for those who are not in dire need if they do not expect to be able to repay it.