It is narrated from Sayyiduna Hujr bin Qays (may Allah be pleased with him), who had lived in the Jahiliyyah (pre-Islamic era): Sayyiduna Ali (may Allah be pleased with him) asked the Messenger of Allah (peace and blessings be upon him) for the hand of Sayyidah Fatimah (may Allah be pleased with her), and he (peace and blessings be upon him) said: "She is yours, on condition that you treat her well."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3557
Musa bin Qays al-Hadrami (may Allah have mercy on him) said: I heard Hujr bin Anbas - he used to eat blood in the Jahiliyyah (pre-Islamic era), and he took part with Sayyiduna Ali (may Allah be pleased with him) in the Battles of the Camel and Siffin - and he narrated: Sayyiduna Abu Bakr and Sayyiduna Umar (may Allah be pleased with them both) asked for the hand of Sayyidah Fatimah (may Allah be pleased with her), and the Prophet (peace and blessings be upon him) said: "She is for you, O Ali!"
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3558