Hadithcore
Riyad as-Salihin, 1266

Umm 'Umarah Al-Ansariyah (May Allah be pleased with her) reported:

Once the Prophet (ﷺ) visited us and I served him some food. He (ﷺ) asked me to eat. I replied that I was observing (optional) fast. He (ﷺ) said, "When people eat by a person observing fast, the angels keep asking Allah's forgiveness for that person until they have had their fill." <b>[At-Tirmidhi]</b>.

وعن أم عمارة الأنصارية، رضي الله عنها أن النبي صلى الله عليه وسلم دخل عليها فقدمت إليه طعامًا فقال ‏"‏ كلي‏"‏ فقالت‏:‏ إني صائمة، فقال رسول الله صلى الله عليه وسلم‏:‏ ‏"‏إن الصائم تصلي عليه الملائكة إذا أكل عنده حتى يفرغوا‏"‏ وربما قال‏:‏ ‏"‏حتى يشبعوا‏"‏ ‏(‏‏(‏رواه الترمذي وقال‏:‏ حديث حسن‏)‏‏)‏‏.‏

References1 variant
In-Book Reference
Book 8, Hadith 276
Sharh · explanationclick to expand
<b>Guidance from the Hadiths:</b><br> 1) They show the merit of serving food to a fasting person at the time of breaking the fast. By virtue of doing so, the angels invoke Allah’s blessings and mercy for the host.<br> 2) It is recommended to supplicate for a person who has entertained fasting people. They demonstrate the supplication to be made by the guest for his host.<br> 3) The Shariah pays attention to etiquette and is careful to reward good-doers so that people will feel motivated to do good. A case in point is the refined etiquette of supplication to be said by a fasting person for the host who provided him with food to break his fast.<br> Note:<br> The Hadith reported by Um ‘Umārah al-Ansāriyyah is inauthentic. Yet there is an authentic Hadith carrying a similar meaning. It was narrated by Ibn Abi Shaybah that ‘Abdullāh ibn ‘Amr said: “When people eat in the house of a fasting person, the angels send blessings upon him.” This statement is regarded as attributed to the Prophet (may Allah’s peace and blessings be upon him), because a Companion would not say such things merely on the basis of his personal opinion. This is emphasized by the Hadith on the supplication to be said by the guest: “May the fasting people break their fast in your house; and may the angels ask forgiveness and mercy for you!”