Musnad Abu Ya'la al-Mawsili 110:155

Abu Khaythama narrated to us, Abbad narrated to us, al-Hajjaj informed us, from al-Hakam, from Miqsam, from Ibn Abbas: That the Prophet, peace and blessings of Allah be upon him, proposed to Maymunah, so she placed her affair in the hands of al-Abbas, and the Prophet, peace and blessings of Allah be upon him, married her.