Sayyidah Umm Umarah bint Ka'b (may Allah be pleased with her) narrates that the Messenger of Allah (peace and blessings be upon him) came to her, and she offered him food. He (peace and blessings be upon him) said to her: "You eat." She said: I am fasting. So he (peace and blessings be upon him) said: "When food is eaten in the presence of a fasting person, the angels pray for him until he finishes," or he said: "until they finish their eating."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8513