Musnad Ahmad 28:139

Hassan narrated to us, Ibn Lahi'ah narrated to us, Huyayy ibn Abdullah narrated to me, from Abu Abd al-Rahman al-Hubuli, who narrated to him from Abdullah ibn Amr, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, in Paradise there is a chamber whose exterior is seen from its interior, and its interior is seen from its exterior." Abu Musa al-Ash'ari said: "For whom is it, O Messenger of Allah?" He said: "For him who softens speech, feeds food, and spends the night standing for Allah while the people are asleep."