On the authority of Abu Sa'id al-Khudri (may Allah be pleased with him), who said that the Messenger of Allah (PBUH) said: Paradise and Hell-fire disputed together, and Hell-fire said: In me are the mighty and the haughty. Paradise said: In me are the weak and the poor. So Allah judged between them, [saying]: You are Paradise, My mercy; through you I show mercy to those I wish. And you are Hell-fire, My punishment; through you I punish those I wish, and it is incumbent upon Me that each of you shall have its fill.
It was related by Muslim (also by al-Bukhari and at-Tirmidhi).