The Prophet ﷺ ruled that a lifetime gift passes to the heir.
حدثنا هشام بن عمار حدثنا سفيان عن عمرو بن دينار عن طاوس عن حجر المدري
أن النبي ﷺ جعل العمرى للوارث
No references are available.
[Its chain of transmission is sahih]. Abu Dawud narrated it in "The Book of Business Transactions," chapter on the ruqba, hadith no. 3559, from the hadith of Amr bin Dinar with this wording. Ibn Hibban graded it sahih, and it is documented in Musnad Humaydi, hadith no. 399, in my edition.