Revelation 20:1-3

Then I saw a mighty angel descending from the heavenly realm, holding a heavy chain and a key—the key of the deep. He seized the dragon, that ancient serpent known as the devil and Satan, and bound him for a thousand years. The mighty angel threw him into the pit, locked it, and sealed it so that he could no longer deceive the nations until the thousand years were over. (After that he must be loosed for a brief time.)