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].
App reference: Book 3, Hadith 11
Arabic/English book reference: Book 3, Hadith 738