Sahih Bukhari Volume 001, Book 003, Hadith Number 115.
Narated By Um Salama : One night Allah's Apostle got up and said, "Subhan Allah! How many afflictions have been descended tonight and how many treasures have been disclosed! Go and wake the sleeping lady occupants of these dwellings (his wives) up (for prayers). A well-dressed (soul) in this world may be naked in the Hereafter."