Musnad Abu Ya'la al-Mawsili 152:86

Abu Khaythama narrated to us, Jarir narrated to us, from Yahya al-Jabir, from Abu Majida, from Abdullah, who said: We asked the Prophet, peace and blessings of Allah be upon him, about walking with the funeral procession. He said: "The walking should be at a pace less than a trot. If it is good, you are hastening it toward it; and if it is otherwise, then away with the people of the Fire." The funeral procession is to be followed, and whoever precedes it is not of it.