Does the brother have the right to demand the annulment of a contract for selling a portion of the mother's inheritance to her daughter, knowing that the mother had instructed the girl to build a mosque on a portion of the land gifted to her?

A bequest to an heir is not valid unless approved by the remaining heirs. As for a bequest for building a mosque, it is valid and is executed from one-third of the estate. In the case of a gift to children during one's lifetime, justice must be observed among them. If some children are favored, it is preferable for the favored child to return what he was favored with. Most scholars are of the opinion that the gift has become established, and the remaining heirs do not have the right to demand its return. Ibn Taymiyyah, however, is of the sole opinion that the favored child should return it after death.