What is the ruling of Islamic law regarding a son's demand for 14,000 dinars in exchange for building two apartments in his deceased father's building, knowing that he has been living in them for many years without paying rent, and his father had previously gifted him a plot of land and a car?

If a father singles out one of his children with a gift, excluding the rest of their siblings, the enforceability of this gift after his death is a matter of dispute: - The majority of scholars hold that the gift is enforceable and binding, and the remaining heirs have no right to revoke it, though it is recommended to return it to the inheritance. - Some meticulous scholars, such as Sheikh al-Islam Ibn Taymiyyah, are of the view that the gift must be returned to the inheritance after the father's death, or during his lifetime if he is still alive.

As for the apartment that the son built on the fourth floor with his own money: - If the father gifted the rooftop to his son for building upon it, or if custom dictates that permission to build is a gift, then the apartment belongs to the son, and the rulings concerning other gifts apply to it, in terms of the recommendation or obligation to return it to the inheritance. - If the father did not gift the rooftop to his son but lent it to him, or permitted him to build without transferring ownership, then this loan ends with the father's death, and the son is entitled to the value of what he built as dismantled material, not as a standing structure. This is the view of the Maliki school.