Musnad Ahmad 1218:0

Narrated to us by Abd al-Rahman, from Sufyan, from al-A’mash, from Abu Salih, from Abu Hurairah, who said: The Messenger of Allah (ﷺ) said: "The fire of the children of Adam, which you kindle, is one part out of seventy parts of the fire of Hell." They said: "O Messenger of Allah, by Allah, it would have been sufficient." He said: "It has been increased over it by sixty-nine parts, each of them like its heat."