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) ruled concerning the umra that it belongs to the one to whom it is given, both during his life and after his death.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4924