4 I saw thrones. Those put in charge of judgment sat on the thrones. I also saw the souls of those beheaded because of their witness to Jesus and the Word of God, who refused to worship either the Beast or his image, refused to take his mark on forehead or hand - they lived and reigned with Christ for a thousand years! 5 The rest of the dead did not live until the thousand years were up. This is the first resurrection - 6 and those involved most blessed, most holy. No second death for them! They're priests of God and Christ; they'll reign with him a thousand years.
Matthew Henry's Commentary on Revelation 20:4-6
Commentary on Revelation 20:4-6
(Read Revelation 20:4-6)
Here is an account of the reign of the saints, for the same space of time as Satan is bound. Those who suffer with Christ, shall reign with him in his spiritual and heavenly kingdom, in conformity to him in his wisdom, righteousness, and holiness: this is called the first resurrection, with which none but those who serve Christ, and suffer for him, shall be favoured. The happiness of these servants of God is declared. None can be blessed but those that are holy; and all that are holy shall be blessed. We know something thing of what the first death is, and it is very awful; but we know not what this second death is. It must be much more dreadful; it is the death of the soul, eternal separation from God. May we never know what it is: those who have been made partakers of a spiritual resurrection, are saved from the power of the second death. We may expect that a thousand years will follow the destruction of the antichristian, idolatrous, persecuting powers, during which pure Christianity, in doctrine, worship, and holiness, will be made known over all the earth. By the all-powerful working of the Holy Spirit, fallen man will be new-created; and faith and holiness will as certainly prevail, as unbelief and unholiness now do. We may easily perceive what a variety of dreadful pains, diseases, and other calamities would cease, if all men were true and consistent Christians. All the evils of public and private contests would be ended, and happiness of every kind largely increased. Every man would try to lighten suffering, instead of adding to the sorrows around him. It is our duty to pray for the promised glorious days, and to do every thing in our public and private stations which can prepare for them.