Is it permissible to disinherit a wealthy son because he refuses to help his needy father, and is it permissible for the father to bequeath one-third of his agricultural land to this son's brothers?

It is not permissible for a father to disinherit one of his children or to bequeath his estate to some heirs to the exclusion of others, due to the Prophet's (peace be upon him) saying: "Fear Allah and be just among your children," and his saying: "Indeed, Allah has given every rightful person his due right, so there is no will for an heir." This is also because Allah has forbidden causing harm through a will.

As for the wealthy son's refusal to spend on his poor father, this is a forbidden matter, and spending on him is obligatory. If the father is poor and his earnings are insufficient, then the completion of the expenditure becomes obligatory on his wealthy son, without any disagreement among scholars.

The expenditure for a poor father is distributed among all his children, both male and female, according to the financial situation of each one of them.