Mishkat al-Masabih

Abu Huraira reported God’s messenger as saying, “When one of you is invited to a meal at a time when he is fasting he should say he is fasting.” In a version he said, “When one of you receives an invitation he should accept it. If he is fasting he should pray, but if not, he should eat.” Muslim transmitted it.

وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: " إِذَا دُعِيَ أَحَدُكُمْ إِلَى طَعَامٍ وَهُوَ صَائِمٌ فَلْيَقُلْ: إِنِّي صَائِمٌ ". وَفِي رِوَايَةٍ قَالَ: «إِذَا دُعِيَ أَحَدُكُمْ فَلْيُجِبْ فَإِنْ كَانَ صَائِمًا فَلْيُصَلِّ وَإِن كَانَ مُفطرا فيطعم» . رَوَاهُ مُسلم