Musnad Abu Ya'la al-Mawsili 155:139

And from Abu Hurairah, from the Prophet, may Allah bless him and grant him peace, he said: A funeral procession passed by him, and they praised it with good in the virtues of goodness. He said: So he said, "It has become incumbent." Then another passed by him, and they praised it with evil in the virtues of evil. He said: So he said, "It has become incumbent." Then he said: "You are the witnesses of Allah on the earth."