Musnad Abu Ya'la al-Mawsili 214:3

Abu Khaythama narrated to us, Abd al-Rahman ibn Mahdi narrated to us, from Sufyan, from Salim Abu al-Nadr, from Umayr, the freed slave of Umm al-Fadl, from Umm al-Fadl: That they disputed regarding the fasting of the Messenger of Allah (may Allah bless him and grant him peace) on the day of Arafah. So she sent a vessel of milk to him, and he drank it.