Musnad Ahmad 1153:609

Muhammad ibn Idris narrated to us, he said: Abd al-Aziz narrated to us, from Yazid, from Muhammad ibn Ibrahim, from Abu Salamah ibn Abd al-Rahman, he said: I asked Aisha, "How much was the dowry of the Messenger of Allah, may Allah bless him and grant him peace?" She said: "His dowry for his wives was twelve uqiyah and a nash." She said: "Do you know what a nash is?" I said: "No." She said: "Half an uqiyah. So that is five hundred dirhams. This was the dowry of the Messenger of Allah, may Allah bless him and grant him peace, for his wives."