Shu'bah bin al-Hajjaj شعبة بن الحجاج · The Book of ar-Ruqba

"Ruqba and 'Umra are not permissible; whoever is given something on the basis of 'Umra, it is his, and whoever is given something on the basis of Ruqba, it is his."

"'Umra and Ruqba are not proper. Whoever gives something on the basis of 'Umra or Ruqba, it belongs to the one to whom he gave it on that basis, both during his lifetime and after his death." Hanzalah narrated it in Mursal form.