Musnad Abu Ya'la al-Mawsili 150:402

'Amr al-Naqid narrated to us, Hushaym ibn Bashir narrated to us, from Hajjaj, from al-Zuhri, from 'Urwah, from 'Aishah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "There is no marriage except with a guardian." Hushaym said: "And the ruler is the guardian for the one who has no guardian."