Sahih Bukhari
Praying at Night in Ramadaan (Taraweeh)
Volume: 003 / Book Number: 032 / Hadith Number: 237
Narrated 'Aisha:
Allah's Apostle used to practice Itikaf in the last ten nights of Ramadan and used to say, "Look for the Night of Qadr in the last ten nights of the month of Ramadan ,"