Musnad Ahmad 30:3705

Muhammad ibn Ubayd narrated to us, Muhammad—meaning Ibn Amr—narrated to us, from Abu Salamah, from Abu Hurayrah, who said: A funeral passed by the Messenger of Allah, may Allah bless him and grant him peace, and they praised it with good, from the virtues of goodness. The Messenger of Allah, may Allah bless him and grant him peace, said: "It has become incumbent; you are the witnesses of Allah upon the earth." Then another funeral passed by him, and they praised it with evil, from the vices of evil. The Messenger of Allah, may Allah bless him and grant him peace, said: "It has become incumbent; you are the witnesses of Allah upon the earth."