Volume 3 · Book 32 · Hadith 6850
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 ,"
— Sahih Bukhari, Volume 3, Book 32: Praying at Night in Ramadaan (Taraweeh), Hadith #6850