Hiban bin Hilal حبان بن هلال · The Book of ar-Ruqba

"My father narrated to us: Ubaidullah -he is, Ibn 'Amr- narrated to us, from Sufyan, from Ibn Abi Najih, from Tawus, from Zaid bin Thabit, that the Prophet said: 'Ar-Ruqba is permissible.'"

"'Umra and Ruqba are the same."

"'Umra (a gift given for life) belongs to the heir."