حَدَّثَنَا عَبْدُ اللَّهِ بْنُ سَعِيدٍ، حَدَّثَنَا أَبُو خَالِدٍ، عَنْ هِشَامٍ، عَنِ ابْنِ سِيرِينَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ إِذَا دُعِيَ أَحَدُكُمْ فَلْيُجِبْ فَإِنْ كَانَ مُفْطِرًا فَلْيَطْعَمْ وَإِنْ كَانَ صَائِمًا فَلْيُصَلِّ ‏"‏ ‏.‏ قَالَ هِشَامٌ وَالصَّلاَةُ الدُّعَاءُ ‏.‏ قَالَ أَبُو دَاوُدَ رَوَاهُ حَفْصُ بْنُ غِيَاثٍ أَيْضًا عَنْ هِشَامٍ ‏.‏

Abu Hurairah reported the Messenger of Allah (PBUH) as saying: When one of you receives an invitation (for a meal), he should accept it. If he isn to fasting, he should eat, and if he is fasten, he should pray. Hisham said: The word salat means to pray (for him to Allah). Abu Dawud said: This tradition has also been narrated by Hafs b. Ghiyath from Hisham. Translation Not Available

Book Ref: Sunan Abi Dawud Book 14 Hadith 2460
Web Ref:  Sunan Abi Dawud Book 13 Hadith 2454