The First Resurrection

Revelation 20:4-6 ESV
Then I saw thrones, and seated on them were those to whom the authority to judge was committed. Also I saw the souls of those who had been beheaded for the testimony of Jesus and for the word of God, and those who had not worshiped the beast or its image and had not received its mark on their foreheads or their hands. They came to life and reigned with Christ for a thousand years. 5 The rest of the dead did not come to life until the thousand years were ended. This is the first resurrection. 6 Blessed and holy is the one who shares in the first resurrection! Over such the second death has no power, but they will be priests of God and of Christ, and they will reign with him for a thousand years.

For those who placed their faith in the testimony of Jesus and the word of God, and did not follow after the beast, they came to life and reigned with Christ for a thousand years.

So who takes part in the first resurrection and when does it happen?
In verse four we see it is the believers who come to life and reign with Christ. We come to life when we believe and are filled with the life giving Holy Spirit . Verse six tells us that those raised will reign with Him for a thousand years. Verse six also tells us that those who share in the first resurrection are blessed and holy. This can only be the redeemed in Christ, for they alone enjoy this state in Christ. Death has no power over them. They have been freed by the blood of Jesus to be His priests and kings with Christ whose rule will have no end.

The rest of the dead(unbelievers) are not raised until the end of the thousand years. They are raised to face judgement and are destined for the second death.