Hammad bin Salama حماد بن سلمة · 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."