Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) said: "What is the matter with people who give gifts to their sons and then withhold them? If the son of one of them dies, he says: 'My property is with me; I did not give it to anyone.' And if he himself is dying, he says (before his death): 'It belongs to my son; I had given it to him.' Whoever gives a gift to someone and the one to whom it was given does not take possession of it, so that on his death it belongs to his heirs, then that gift is void."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الهبات / 11949