This verse begins with the linking word “therefore.” The loud voice in heaven (Revelation 12:10) now calls upon heaven itself, with all its inhabitants, to rejoice specifically because “the accuser of our brothers” has been expelled. No longer can lies and deceit and slander have a place before God’s throne; Christ Jesus has atoned for sin and so God sees sinners as righteous before him—and he will not tolerate any creature suggesting it is not so! From his courts every vestige of rebellion has been banned, which certainly gives room for joy!
12 Therefore, rejoice, O heavens and you who dwell in them! But woe to you, O earth and sea, for the devil has come down to you in great wrath, because he knows that his time is short!”