Revelation 20:1-3 King James Version (KJV)
20 And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.
2 And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years,
3 And cast him into the bottomless pit, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be fulfilled: and after that he must be loosed a little season.
Revelation 20:1-3 New International Version (NIV)
The Thousand Years
20 And I saw an angel coming down out of heaven, having the key to the Abyss and holding in his hand a great chain. 2 He seized the dragon, that ancient serpent, who is the devil, or Satan, and bound him for a thousand years. 3 He threw him into the Abyss, and locked and sealed it over him, to keep him from deceiving the nations anymore until the thousand years were ended. After that, he must be set free for a short time.