Is it permissible for children to withhold a portion of their extravagant father's inheritance and save it for him without his knowledge, and is it permissible to pay off the father's debt to the maid from this money without his knowledge?

It is permissible to place an interdiction on a father if he is not of sound mind or is profligate (safih), and he should not be allowed control over his wealth. The general rule is that such an interdiction should be by the ruling of a Sharia judge. If this is not possible, it is permissible for the children to safeguard his wealth, prevent him from squandering it, and spend from his money on what serves his best interest, without tyranny or informing him if it is highly probable that he would not approve, and to avoid damaging family relations. This is done while preserving his right to dispose of his wealth in a lawful manner. It is permissible to pay the overdue wages of a housemaid from his money, as this is one of the obligations incumbent upon him. It is not permissible to deposit money in usurious banks except in cases of extreme necessity, provided that no interest is taken.