Abu Hurairah (May Allah be pleased with him) reported:
Messenger of Allah (ﷺ) said, "When any of you is invited to a meal, he should accept the invitation. If he is observing Saum (fasting), he should supplicate for the betterment of the host and if he is not fasting, he should eat."[Muslim]. (ID)
App reference (ID): Book 3, Hadith 11 (ID)
Arabic/English book reference (ID): Book 3, Hadith 738 (ID)