A narration has:

"The life-tenancy which Allah's Messenger (ﷺ) allowed was only that in which one says, 'It is for you and your descendants.' However, if he says, 'It is yours as long as you live', it returns to its owner."

وَفِي لَفْظٍ : { إِنَّمَا اَلْعُمْرَى اَلَّتِي أَجَازَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-أَنْ يَقُولَ: هِيَ لَكَ وَلِعَقِبِكَ، فَأَمَّا إِذَا قَالَ: هِيَ لَكَ مَا عِشْتَ، فَإِنَّهَا تَرْجِعُ إِلَى صَاحِبِهَا } [1]‏ .‏