Musnad Ahmad 30:2688

Yazid narrated to us, Muhammad informed us, from Abu Salamah, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Fire and Paradise disputed. The Fire said: 'The tyrants and the arrogant enter me.' And Paradise said: 'The weak and the poor enter me.' So Allah, the Mighty and Majestic, said to the Fire: 'You are My punishment; I take vengeance through you upon whom I will.' And He said to Paradise: 'You are My mercy; I show mercy through you to whom I will.'"