Musnad Abu Ya'la al-Mawsili 219:1

Abu Khaythama Zuhayr ibn Harb narrated to us, Sufyan ibn 'Uyayna narrated to us, 'Amr narrated to us, from Salim ibn Shawwal, from Umm Habiba, who said: "We used to do it during the time of the Messenger of Allah, may Allah bless him and grant him peace," meaning we would pray the morning prayer at Mina on the Day of Sacrifice.