Is it permissible to hoard money that exceeds the husband's needs without his knowledge, in order to use it to buy personal necessities or for the wife's family?

A wife is not permitted to spend from her husband's private money or give anything from it to her family or others, except with his permission. An exception to this is a small amount that is customarily overlooked. The wife must return what she took without her husband's permission, without being obliged to inform him of what she did or to seek his forgiveness for it, while regretting it and resolving not to do it again.