Musnad Abu Ya'la al-Mawsili 150:245

Sarij ibn Yunus narrated to us, Ali ibn Thabit narrated to us, Mandil narrated to us, from Hisham ibn Urwah, from Urwah, from Aisha, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no marriage except with a guardian, and the sultan (ruler) is the guardian for the one who has no guardian."