It is not permissible for a woman to take anything from her husband’s wealth without his permission, unless he is falling short in his spending on her, in which case it is permissible for her to take what is sufficient for her and her children on a reasonable basis, as the Prophet (peace and blessings of Allaah be upon him) said to Hind bint ‘Utbah when she complained to him that her husband Abu Sufyaan was falling short in his spending on her and on her children. He said to her: “Take what is sufficient for you and your children on a reasonable basis.” There is no kafaarah required for that if the situation is as we have described. But if she takes when there is no shortcoming on his part, then she has to return what she took even if that is without his knowledge, if she is afraid that telling him will make him angry with her. 

May Allaah send blessings and peace upon our Prophet Muhammad and his family and companions.