It is narrated from Sayyidah Umm Umarah bint Ka'b (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) came to her, and she had food brought for him (peace and blessings be upon him). He (peace and blessings be upon him) invited her to eat with him as well, and she said: "I am fasting." He (peace and blessings be upon him) said: "When people eat food in the house of a fasting person, the angels keep praying for him until they complete their meal and finish."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21512