Musnad Ahmad 25:1173

Affan narrated to us, Hammad ibn Salamah narrated to us, Abdullah ibn Uthman ibn Khuthaym narrated to us, from Sa’id ibn Jubayr, from Ibn Abbas: That the Messenger of Allah (peace and blessings of Allah be upon him) was in the house of Maymunah, and she placed water for his ablution for him during the night. She said: "O Messenger of Allah, Abdullah ibn Abbas placed this for you." He said: "O Allah, grant him understanding in the religion and teach him the interpretation."