Sunan an-Nasa'i 1910
It was narrated from Abu Hurairah, who attributed it to the Prophet:
"Hasten with the Janazah, for if it was righteous then your are taking it toward something good, and if it was otherwise, then it is an evil of which you are relieving yourselves."
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ سَعِيدٍ، عَنْ أَبِي هُرَيْرَةَ، يَبْلُغُ بِهِ النَّبِيَّ صلى الله عليه وسلم قَالَ ‏
"‏ أَسْرِعُوا بِالْجَنَازَةِ فَإِنْ تَكُ صَالِحَةً فَخَيْرٌ تُقَدِّمُونَهَا إِلَيْهِ وَإِنْ تَكُ غَيْرَ ذَلِكَ فَشَرٌّ تَضَعُونَهُ عَنْ رِقَابِكُمْ ‏"‏ ‏.‏