Sahih Muslim Book 40, Hadith Number 6821.
Hammam b. Munabbih reported that Abu Huraira narrated to them some ahadith of Allah’s Messenger (may peace be upon him) and one of them is this that Allah’s Messenger (may peace be upon him) said: The Paradise and the Hell fell into dispute and the Hell said: I have been distinguished for accommodating (the haughty and proud in me), and the Paradise said: What is the matter that the meek and the humble and the downtrodden and simple would find an abode in me? Thereupon Allah said to Paradise: You are a (means) of My Mercy. I shall show mercy through you to one whom I will from amongst My servants. And Allah said to the Hell: You are a (sign) of My chastisement and I shall chastise through you anyone whom I will from amongst My servants and both of you, would be full. And as regards the Hell it would not be full until Allah, the Exalted and Glorious, places His foot therein, and it would say: Enough, enough, enough, and it would be then full and the one part would draw very close to the other one and Allah would not treat unjustly anyone amongst His creation and He would create another creation for the Paradise (to accommodate it).