Praying at Night in Ramadaan (Taraweeh)

Bukhari :: Book 3 :: Volume 32 :: Hadith 238

Narrated Ibn Abbas:

The Prophet said, "Look for the Night of Qadr in the last ten nights of Ramadan ,' on the night when nine or seven or five nights remain out of the last ten nights of Ramadan (i.e. 21, 23, 25, respectively)."