The lifetime grant that the Messenger of Allah ﷺ permitted is when one says, "It is yours and your descendants'." But if he says, "It is yours for as long as you live," then it returns to its original owner.Muamar said, Zuhri used to issue legal rulings based on this.
إنما العمري التي أجاز رسول الله ﷺ أن يقول هي لك ولعقبك. فأما إذا قال: هي لك ما عشت. فإنها ترجع إلى صاحبها. قال معمر: وكان الزهري يفتي به.
Muslim narrated it in the Book of Gifts (1625: 23) through several routes from Abdul-Razzaq, who said, Mamar informed us from Zuhri, from Abu Salama, from Jabir, and he related it. Jabir used to hold this view. Zuhri used to give legal rulings based on it, and it is the view of Malik. It is also related from him that he said, "The umra grant transfers ownership of the usufruct, not the property itself."Abu Ubayd Harawi said, "Malik used to say, if a man grants another man a house as an umra, saying, 'This is yours for your lifetime,' then it remains subject to that condition, so when the recipient of the grant dies, it reverts to the grantor, unless he says, 'This is yours and for your descendants after you.'" (Gharib al-Hadith 2/79)