Musnad Ahmad 30:3071

Waki' narrated to us, from Hammad, from Muhammad, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "This fire of yours is one part out of seventy parts of the fire of Hell." A man said: "It is surely sufficient, O Messenger of Allah." He said: "It has been made to exceed it by sixty-nine parts, each of them being heat."