Is it permissible for a father to stipulate in his will that a specific amount of his money be divided among all his heirs, and to designate his male children for the remainder of the estate, which increased through their efforts after the father's death, knowing that the father is of sound mind?

A bequest to an heir is invalid unless approved by the other heirs, because the Prophet, peace and blessings be upon him, said: "Indeed, Allah has given every rightful person his right, so there is no bequest to an heir." Therefore, the father's aforementioned bequest is not valid, and the money becomes an inheritance to be divided among all heirs.

However, it is permissible for the father to give a immediate, handed-over gift to his working children before his death if there is a valid justification, such as the children's work in their father's business and their contribution to increasing his wealth being a justification for this, unless their efforts were for a wage, in which case it is not permissible to prefer them over the daughters.