Musnad Ahmad 5:768

Abdullah narrated to us, Abbad ibn Ya'qub al-Asadi Abu Muhammad narrated to me, Muhammad ibn Fudayl narrated to us, from Abd al-Rahman ibn Ishaq, from al-Nu'man ibn Sa'd, from Ali, may Allah be pleased with him, who said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "Indeed, in Paradise there are chambers whose interiors are seen from their exteriors, and their exteriors are seen from their interiors." A Bedouin said: "O Messenger of Allah, for whom are they?" He said: "For those who spoke kindly, fed the hungry, and prayed to Allah at night while the people were sleeping."