Q. At the end of the millennium, God releases Satan from the lake of fire. Why? Where do we find more information about this in the scriptures?
A. God actually releases Satan from his imprisonment in the Abyss. (Rev. 20:3) I believe this is part of God’s purpose for the Millennium. Think about it. Why a 1000 year interlude between time and eternity? I think it’s to answer three accusations man has hurled at God through the ages.
In justifying his sinfulness man has said,
1) “The devil made me do it.” So the devil is bound for 1000 years.(Rev. 20:3)
2) “It’s the influence of all those unbelievers.” So at the beginning of the Millennium, all unbelievers are taken from Earth.(Matt. 25:41)
3) “It’s because you went away and left us.” So God comes to Earth to rule in person from Jerusalem.(Ezek. 43:7)
After 1000 years of perfect in person rule with the devil bound, what’s the outcome?
When the thousand years are over, Satan will be released from his prison and will go out to deceive the nations in the four corners of the earth–Gog and Magog–to gather them for battle. In number they are like the sand on the seashore. They marched across the breadth of the earth and surrounded the camp of God’s people, the city he loves. But fire came down from heaven and devoured them. (Rev. 20:7-9)
That’s all we’re told, but here’s my opinion.
Remember, at the beginning of the Millennium Tribulation Survivors who become believers after the Church is Raptured come into the Kingdom in their natural states to re-populate the planet. Their children are the ones who Satan recruits. Even after 1000 years of perfect rule by the Lord Himself, there’s still enough rebellion in the hearts of natural man that as soon as Satan’s released they rise up in arms against the Almighty.
I think the whole purpose of the Millennium is to demonstrate that there’s no condition possible under which natural man can live in peace with God. Satan is released to help prove this point.