Musnad Abu Ya'la al-Mawsili 150:188

Abu Kurayb narrated to us, Ibn al-Mubarak narrated to us, from Hajjaj, from al-Zuhri, from Urwah, from Aisha, from the Prophet, may God bless him and grant him peace. And from Hajjaj, from Ikrimah, from Ibn Abbas, they both said: The Prophet, may God bless him and grant him peace, said: "There is no marriage except with a guardian." And in the hadith of Urwah: "And the Sultan is the guardian of the one who has no guardian."