Musnad Abu Ya'la al-Mawsili 220:1

Ali ibn al-Ja'd narrated to us, Shu'bah informed us, from Habib ibn Zayd al-Ansari, who said: I heard a freedwoman of ours, who is called Layla, narrating from Umm 'Amarah bint Ka'b: That the Messenger of Allah (peace and blessings of Allah be upon him) entered upon her, so she called for food for him. He said: "Come and eat." She said: "I am fasting." He said: "Indeed, when the fasting person has food eaten in his presence, the angels pray for him."