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.  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا دُعِيَ أَحَدُكُمْ فَلْيُجِبْ فَإِنْ كَانَ صَائِمًا فَلْيُصَلِّ وَإِنْ كَانَ مُفْطِرًا فَلْيَطْعَمْ