Does a divorce issued by a husband to his wife—whom he had previously divorced twice—in the form of "You are divorced if you do not bring the money you have" take effect, knowing that the wife has the money but claims not to possess it, and is it permissible for her to leave the marital home in this situation?

It is not permissible for your sister's husband to take anything from her money except with her consent, due to the Prophet's (peace be upon him) saying: "The wealth of a Muslim person is not lawful except with his willing consent." Your sister is not obliged to fulfill his request. However, if she does not give him the money he requested, she would have caused him to break his oath, and based on this, divorce would occur absolutely according to the view of the majority, whether the husband intended to cause it or intended to threaten, and so on. This is the jurisprudential ruling on which fatwas are issued.

One must be cautious with divorce pronouncements to preserve the cohesion and stability of the family and to spread affection and mercy between the spouses.