Hisgalus 20:1-3

And I saw a malach (an angel) coming down out of Shomayim having the mafte'ach (key) of the Tehom (Abyss) and a great chain in his hand, And he seized the Dragon, the NACHASH HaKadmoni, who is Malshin and HaSatan. And he bound him for elef shanim (one thousand years), And threw him into the Tehom (Abyss), and shut and sealed it over him that he could not deceive any more the Goyim until the elef shanim (thousand years) were completed. After these things it is necessary for him to be released a short time.