Musnad Abu Ya'la al-Mawsili 244:2

Abu Bakr narrated to us, Waki' narrated to us, from Musa ibn 'Ali, from his father, from Abu Qays, the freed slave of 'Amr ibn al-'As, from 'Amr, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The distinction between our fasting and the fasting of the People of the Book is the meal of the suhur."