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: "Whoever gives someone an umra, it belongs to him, both during his life and after his death. Do not make the condition of ruqba; whoever does so, it will follow the path of inheritance."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4929