What is the ruling on a father writing land to his grandchildren or retracting a gift, and is it permissible to favor some children in giving gifts?

What the man did is considered a bequest (wasiyyah (definition)), which is not valid for an heir, nor for more than one-third of the estate, unless approved by the adult heirs. If the son of the son is an heir due to the absence of direct sons for the deceased, then the bequest is invalid, according to the Prophet’s (peace be upon him) saying: "Indeed, Allah has given every rightful person his right, so there is no bequest for an heir." If he is not an heir, then the bequest is valid as long as it does not exceed one-third, or if the heirs approve it.

If the writing constitutes an immediate gift (hiba najizah) and possession has been taken, then it is valid, and the sons have no right to object. The giver is not permitted to revoke his gift after it has been taken possession of, based on the Prophet’s (peace be upon him) saying: "One who revokes his gift is like one who revokes his vomit." However, if it was a bequest, it is permissible to revoke it.

A grandfather's writing to his daughters' children, whether as a gift or a sale, is permissible if possession has been taken. If the intention was to disinherit the heirs, or if the matter was conditional upon the grandfather's death, then the bequest is limited to one-third, unless the heirs permit an increase.