What is the ruling on a father withdrawing money from investment certificates because their returns are unlawful, and then sending his wife and son for 'Umrah with it? And will the son and mother be held accountable for the travel expenses, knowing that the questioner is aware the mother has her own money?

Agency is based on trustworthiness. An agent is not permitted to act except in what is in the best interest of the principal. If he acts in a way that goes against that interest due to negligence, he is liable. Any amount exceeding the principal from withdrawing investment certificates from a usurious bank is not permissible to own; rather, it must be disposed of by spending it on the poor, the needy, and general Muslim welfare, in accordance with Allah's saying: ﴿And if you repent, you may have your principal – [thus] you do not wrong, and you are not wronged.﴾ [Al-Baqarah: 279].

Regarding Umrah (definition): 1. If the illness did not affect the father's mental capacity: If what you did was with the father's knowledge and approval, then there is nothing on you, because the action is attributed to him, and he is the owner of the money. If it was without the father's knowledge, while he had full capacity, then the agent (the son) bears all the expenses he spent on his brother and mother, and he can claim them back from them. As for the money he spent on his father for Umrah, the father is obligated to pay it according to those who deem Umrah obligatory, and likewise the expense of the companion. If the father had performed Umrah before, he is not obligated to perform another. If the son performed Umrah for him without his permission to spend from his money, the son bears the cost.

2. If the illness affected the father's mental capacity and deprived him of it: You must bear all the expenses you spent on him, your brother, and your mother, because it is not permissible to dispose of the money of a person who lacks capacity in a way that harms him, even according to the view that Umrah is obligatory, because it is not valid for him in his state of madness, according to the preponderant opinion.

3. If the illness deprived him of the capacity to dispose of his money, yet he is capable of worship: There is no objection to performing the obligatory Umrah for him, but not the supererogatory one. His expenses will be from his money, as well as the expenses of anyone needed to accompany him. Anything beyond that will be borne by the son.