In his vision John saw that Satan’s inability to deceive was limited to (the symbolic) 1000 years (see on Revelation 20:2), at which point he will “be released for a little while.” This is a thread John will briefly drop and then pick up again in Revelation 20:7.
3 and threw him into the pit, and shut it and sealed it over him, so that he might not deceive the nations any longer, until the thousand years were ended. After that he must be released for a little while.