Why, after binding him for a thousand years, is God going to release Satan?

TL;DR:

After Christ's thousand-year reign, God will release Satan to allow those born during the millennial kingdom to choose whether to follow God or rebel. Following this final rebellion, God will punish Satan and his followers, leading to the creation of a new heaven, earth, and eternal life with God.

what does the bible say?

After the thousand-year reign of Christ, God will release Satan to allow those still alive– those born during the millennial kingdom– to make their final decision to follow God or not. Despite the peace and Christ’s visible reign, some people will still rebel. This final release is an opportunity for humanity to make their ultimate choice. After this rebellion, God will punish Satan and his followers,and all who are not in the Book of Life will be removed. The ultimate victory over sin and Satan will prepare the way for a new heaven, earth, and God's eternal dwelling with His people.

from the old testament

Releasing Satan after 1,000 years is not mentioned in the Old Testament.

from the new testament

Revelation 20:7–8 notes, "And when the thousand years are ended, Satan will be released from his prison and will come out to deceive the nations that are at the four corners of the earth, Gog and Magog, to gather them for battle; their number is like the sand of the sea." Following the millennial kingdom (the thousand-year reign of Christ), God will allow Satan to be released and gather unbelievers to battle against the Lord and His people.
At the end of the tribulation period, some people who believed in Jesus during the tribulation will still be alive and will enter the millennial kingdom alive rather than coming from heaven to earth with the Lord. These individuals will marry and have children. Apparently, some of these children will not believe in the Lord and will eventually side with Satan in the final battle following Satan's release in Revelation 20. Many unbelievers will still on the earth at this time, since Revelation 20:8 describes them as "the nations that are at the four corners of the earth, Gog and Magog, to gather them for battle; their number is like the sand of the sea."
God releasing Satan for a short amount of time allows those who are still alive to make their final decision either to follow God or not. At this point, God punishes the Devil, beast, false prophet, and those who follow them. Revelation 20:9–10 states, "Fire came down from heaven and consumed them, and the devil who had deceived them was thrown into the lake of fire and sulfur where the beast and the false prophet were, and they will be tormented day and night forever and ever."
Once Satan and all of those not in the Book of Life are removed, God will be prepared to create a new heaven, new earth, and new holy city (Revelation 21:1–2). Since sin and Satan have been removed, God can now come and live among His people (Revelation 21:3). No curse of sin will continue (Revelation 21:4). All things will be new (Revelation 21:5).

implications for today

The release of Satan after the thousand-year reign of Christ might seem perplexing, but it highlights God's patience in giving everyone an opportunity to turn to Him. Even after such a long period of peace and Christ's visible reign, some individuals will still reject God. By allowing Satan to gather a final rebellion, God gives humanity the opportunity to make their ultimate choice—to follow Him or not. This moment is a powerful reminder that our decisions matter, and we are called to continually choose God, even in times of peace and prosperity. For us today, this reflects the importance of living intentionally in our faith, continually choosing righteousness over rebellion. It's easy to take God's grace for granted in times of ease, but knowing that this moment of final judgment is coming reminds us to be vigilant in our walk with Him and to share the gospel with urgency while there is still time. The ultimate victory over sin and Satan, culminating in a new heaven and earth, promises that evil will one day be fully vanquished, and God's people will live with Him forever. We live with the assurance of victory that we can be part of as we live God-honoring today.

understand

God will release Satan after the thousand-year reign to allow final choices for those born during the millennium.
The release of Satan after the thousand-year reign leads to a final rebellion where Satan's followers battle against God.
After the rebellion, God will punish Satan and his followers and create a new heaven and earth for His people.

reflect

How does the idea of a final decision for humanity, even after a thousand years of peace, challenge your understanding of free will and God's sovereignty?
How can you ensure you are consistently choosing to follow God, even during times of peace and ease in your life?
How does the promise of God's ultimate victory over sin and Satan impact your daily life and hope for the future?

engage

What do we learn about God's character through His decision to release Satan after the thousand-year reign?
How can we encourage others to live intentionally in their faith, knowing that a final judgment is coming?
What practical steps can we take to avoid complacency in our walk with God, especially in times of peace and prosperity?