Majma al-Zawaid — Hadith 18767

Sayyiduna Abdullah bin Amr (may Allah be pleased with him) narrates this saying of the Prophet (peace and blessings be upon him): "Indeed, in Paradise there are upper chambers whose outside can be seen from the inside and whose inside can be seen from the outside." Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) asked: "O Messenger of Allah, for whom are they?" The Prophet (peace and blessings be upon him) said: "For the one who speaks gently, feeds others, and spends the night standing before Allah Almighty (in prayer) while people are asleep."
Imam Ahmad recorded it, and its narrators have been declared trustworthy, although there is weakness in some of them. (Allamah al-Haythami says:) I say: Some hadiths on this theme have already passed in the chapter on the virtue of voluntary prayers.