once
((إِذَا دُعِيَ أَحَدُكُمْ فَلْيُجِبْ، فَإِنْ كَانَ صَائِماً فَلْيُصَلِّ، وَإِنْ كَانَ مُفْطِراً فَلْيَطْعَمْ)) ، وَمَعْنَى فَلْيُصَلِّ أَيْ فَلْيَدْعُ.
Meaning
If you are not invited (to a meal) then answer. If you happen to be fasting, then supplicate (for those present) and if you are not fasting, then eat.
Source and references
Hisn al-Muslim, entry 185.The reference is copied from the edition; separate editorial verification is not complete yet.
Source edition: Fortress of the Muslim. Open source ↗