It is narrated from Sayyiduna Zayd bin Thabit (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Do not make the condition of ruqba; whoever makes the condition of ruqba on anything, it will be upon the path of inheritance."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4930