Sahih Muslim 1431
Sahih Muslim · Book 16: The Book of Marriage · The command to accept invitations
Abu Haraira (Allah be pleased with him) reported Allah's Messenger (ﷺ) as saying:
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ ، حَدَّثَنَا حَفْصُ بْنُ غِيَاثٍ ، عَنْ هِشَامٍ ، عَنِ ابْنِ سِيرِينَ ، عَنْ أَبِي هُرَيْرَةَ ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا دُعِيَ أَحَدُكُمْ فَلْيُجِبْ فَإِنْ كَانَ صَائِمًا فَلْيُصَلِّ وَإِنْ كَانَ مُفْطِرًا فَلْيَطْعَمْ " .
If any one of you is invited, he should accept (the invitation). In case he is fasting, he should pray (in order to bless the inmates of the house), and if he is not fasting he should eat.