Narrated Abu Hurayrah Ahmad and Nasa'i [ transmitted it.]:
Allah's Messenger said, "Ramadan, a blessed month, has come to you during which Allah has made it obligatory for you to fast. In it the gates of Heaven are opened, the gates of al-Jahim are locked, and the rebellious devils are chained. In it Allah has a night which is better than a thousand months. He who is deprived of its good has indeed suffered deprivation."
Tirmidhi, Number 1962 I