Sunan Abi Dawud, Hadith 3162

Narrated Abu Hurairah: If anyone attends the funeral and prays over (the dead), he will get the reward of one qirat, and if anyone attends the funeral until the completion (of the burial), he will get the reward of two qirats, the smaller of them being equivalent of Uhud, or one of them being equivalent to Uhud.

حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا سُفْيَانُ، عَنْ سُمَىٍّ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، يَرْوِيهِ قَالَ مَنْ تَبِعَ جَنَازَةً فَصَلَّى عَلَيْهَا فَلَهُ قِيرَاطٌ وَمَنْ تَبِعَهَا حَتَّى يُفْرَغَ مِنْهَا فَلَهُ قِيرَاطَانِ أَصْغَرُهُمَا مِثْلُ أُحُدٍ أَوْ أَحَدُهُمَا مِثْلُ أُحُدٍ ‏.‏

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also referenced under: Hadith 3168 (DarusSalam)