I heard the Messenger of Allah ﷺ say, "Whoever grants another man a lifetime gift for him and his descendants has thereby relinquished his right to it by his own words. It belongs to the one to whom it was given and to his descendants."
سمعت رسول الله ﷺ قال: من أعمر رجلا عمرى له ولعقبه فقد قطع قوله حقه فيها، وهي لمن أعمر والعقبه.