Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) said: "Whatever woman is married on a dowry, a gift or a promise before the marriage contract is concluded, that is hers; and whatever is given after the marriage contract belongs to the one to whom it was given. And the most rightful thing for which a man is honoured is on account of his daughter or his sister."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصداق / 14428