Amr bin Shu'aib bin Muhammad عمرو بن شعيب بن محمد السهمي · The Book of 'Umra

"It is undoubtedly his, and it is not permissible for the giver to stipulate any conditions or exceptions." Abu Salamah said: "Because he gave it as a gift and thus, it is subject to the same ruling as the estate, and the condition (that it will revert to the giver on the death of recipient) has become invalid."

"Any man who gives a lifelong gift to another man, it belongs to him (the recipient) and his descendants. He said: 'I have given it to you and to your descendants so long as any of you are still alive.' So it belongs to the one to whom it was given, and it cannot revert to the first owner, since he has given it as a gift, and as such, it becomes subject to the same ruling as the estate."