Sahih Muslim Book 012, Hadith Number 3972.
Chapter : Al-'Umra (Life grant).
Jabir b. 'Abdullah (Allah be pleased with them) reported Allah's Messenger (may peace be upon him) as saying: Whoever a person is gifted a life grant, then it is for him (belongs to him and to his posterity, for it belongs to him who has been given it). It would not return to him who gave it for he conferred it as a gift (it becomes the property of the donee and as such) rules of inheritance will apply to it.