It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "Ruqba and umra (as conditions) are not permissible; so whoever is given something as ruqba or umra, it becomes his (permanently)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10925