Is it permissible for a father to sell, gift, or bequeath a plot of land or a portion of his property to one of his children to the exclusion of the rest of his children?

A father's bequest to one of his children is invalid because it is a bequest to an heir, unless the other heirs permit it.

It is permissible for a child to buy from or sell to his father, or for his father, just like any other person. If the sale is a sham, it is a gift. If it is for much less than its value, it is a preferential sale (bay' muhabat).

It is permissible for a father to gift to one of his children, provided there is fairness, meaning he gives the others a similar gift, or if there is a legitimate Islamic justification for it, such as poverty or illness, based on the Prophet's (peace and blessings be upon him) saying: "Fear Allah and be just among your children."