Musnad Ahmad 1153:464

Ibrahim ibn Ishaq narrated to us, he said: Ibn al-Mubarak narrated to us, from Hisham ibn Urwah; and Ali ibn Ishaq said: Abdullah informed us, he said: Hisham informed us, from his father, from Aisha, that Sawdah said: "O Messenger of Allah, I have gifted my day to Aisha." So the Messenger of Allah, peace and blessings of Allah be upon him, would divide her day for her.