Sayyidah Umm Umarah (may Allah be pleased with her) said: The Messenger of Allah (peace and blessings be upon him) came to me, and I brought him (peace and blessings be upon him) fruit or food. Some of the people kept apart and did not eat. The Messenger of Allah (peace and blessings be upon him) said: "What is the matter with them?" I said: "They are fasting." He (peace and blessings be upon him) said: "Whenever people who are not fasting eat in the presence of a fasting person, the angels keep praying for mercy for them until evening."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21513