Maliks Muwatta Book 36, Hadith Number 44.
Section : Judgement on Life Pensions.
Malik related to me from Yahya ibn Said that Abd ar-Rahman ibn al-Qasim ibn Muhammad heard Makhul ad-Dimashqi ask al-Qasim ibn Muhammad about the life pension and what people said about it. Al-Qasim ibn Muhammad said, “I have only come upon people who keep to the conditions they make about their property and what they are given.”
Yahya said that he heard Malik say, “What is done in our community is that the life pension reverts to the one who makes it a life pension unless he says, ‘It belongs to you and your posterity.'”