What is the ruling on a father nominally transferring all his property to his son before his death, thereby disinheriting his two daughters and his wife from inheritance?

Giving a deceased person's son all his property is considered a gift (hiba), not a sale, and it has two scenarios:

The first: If the father gave him his property during his lifetime, and he was not suffering from a life-threatening illness. This is a completed gift, and the father sinned by favoring one son, as he was obligated to be just among his children, based on the hadith: "Fear Allah and be just among your children." If the father died before retracting his gift, then the gift is binding according to the majority of scholars, while others believe it is invalid and must be returned.

The second: If the father gave him that while suffering from a life-threatening illness, it is considered a bequest to an heir (wasiyya li-warith), which is religiously prohibited and does not take effect unless the remaining heirs (the two daughters and the wife) consent. If they do not consent, the son must return the property, and it must be distributed according to Islamic law. If he does not do so, the heirs have the right to take the matter to the Sharia court to compel him, for the ruler can deter what the Qur'an does not deter.

If the heirs are the mother, the son, and the two daughters, the mother receives one-sixth due to the presence of a lineal descendant, and the remainder is for the son and the two daughters by way of ta'sib (residuary heirship), with the male receiving the share of two females.