Is a verbal will from a grandfather to his father and uncle regarding a piece of land valid and permissible in Sharia?

An oral will is valid provided there is evidence or confirmation from the heirs, but it cannot be established merely by a claim. A will made to an heir is forbidden by Islamic law and is not executed unless the adult, mature heirs consent, due to the Prophet's (peace be upon him) saying: "Indeed, Allah has given every rightful person his right, so there is no will for an heir." Nevertheless, the aforementioned will is valid if the heirs permit it.