Musnad Ahmad 30:434

Ya'la and Yazid narrated to us, they said: Muhammad ibn 'Amr informed us, from Abu Salamah, from Abu Hurairah, who said: A funeral passed by the Messenger of Allah, may Allah bless him and grant him peace. Yazid said: They passed by the Messenger of Allah, may Allah bless him and grant him peace, with a funeral, and they praised it with good, regarding the virtues of goodness. He said: "It has become incumbent." Then another funeral passed by him, and they praised it with evil, regarding the virtues of evil. He said: "It has become incumbent." Then he said: "You are the witnesses upon the earth."