The Messenger of Allah ﷺ said, "Do not give a property as ruqba, nor as umra. Whoever gives something as ruqba or umra, it belongs to the heirs of the recipient."
أخبرنا محمد بن عبد الله بن يزيد عن سفيان عن ابن جريج عن عطاء
أن رسول الله ﷺ قال لا ترقبوا ولا تعمروا فمن أرقب أو أعمر شيئا فهو لورثته
Sourcing, sahih. Abu Dawud narrated it in the chapter on transactions, in the section on one who says "and for his descendants," hadith no. 3556, from the hadith of Sufyan bin Uyayna, with this wording. It is also in al-Kubra, hadith no. 6563. Ibn Hibban and others graded it sahih. It has other routes of transmission in Muslim and elsewhere. See the earlier hadith no. 3760.