Is it permissible to take money from one's father without his knowledge to cover treatment costs that he refuses to pay in full?

The financial support for the treatment of a child, whether young or old, who is poor and unable to earn, is obligatory upon the father. This is because it falls under the general scope of financial support, and it includes the doctor's fees and the cost of medications. This support is not fixed, as it is obligatory as an act of solace and compassion. It is not permissible to take money without the father's permission, unless he refuses to pay for the treatment costs after being informed. In that case, it is permissible to take the equivalent cost of the treatment without his knowledge.