Isa bin Yonus bin Abi Ishaq عيسى بن يونس بن أبي إسحاق · The Book of 'Umra

"I heard the Messenger of Allah say: 'Whoever gives a life-long gift to a man, it belongs to him and to his heirs; his words (when he gave the gift) put an end to his rights over it, and it belongs to the one to whom it was given on the basis of 'Umra, and to his heirs.'"