بُلُوغُ الْمَرَامِ
Bulugh al-Maram 1041
Marriage
وَعَنْهُ قَالَ : قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ إِذَا دُعِيَ أَحَدُكُمْ فَلْيُجِبْ ; فَإِنْ كَانَ صَائِمًا فَلْيُصَلِّ , وَإِنْ كَانَ مُفْطِرًا فَلْيُطْعَمْ } أَخْرَجَهُ مُسْلِمٌ أَيْضًا [1] .
Narrated [Abu Hurairah (RA)]: Allah's Messenger (ﷺ), "When one of you is invited (to a meal) he must accept. If he is fasting he should pray (i.e. make supplication for the host) and if he is not fasting he should eat." [Muslim reported it too].
Sunnah.com reference: Book 8, Hadith 90