Narrated AbuHurayrah: People with a bier passed by the Messenger of Allah (ﷺ). They (the companions) spoke highly of him. He said: Paradise is certain for him. Then some people with another (bier) passed by him. They spoke very badly of him. He said: Hell is certain for him. He then said: Some of you are witness to others.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، حَدَّثَنَا شُعْبَةُ، عَنْ إِبْرَاهِيمَ بْنِ عَامِرٍ، عَنْ عَامِرِ بْنِ سَعْدٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ مَرُّوا عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم بِجَنَازَةٍ فَأَثْنَوْا عَلَيْهَا خَيْرًا فَقَالَ " وَجَبَتْ " . ثُمَّ مَرُّوا بِأُخْرَى فَأَثْنَوْا عَلَيْهَا شَرًّا فَقَالَ " وَجَبَتْ " . ثُمَّ قَالَ " إِنَّ بَعْضَكُمْ عَلَى بَعْضٍ شُهَدَاءُ " .
sunnah.com