We continue going verse by verse —
(Rev 20:4 ESV) 4 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.
Who reigns with Christ — and when? Well, sometimes the scriptures speak of Christians ruling at the end of time, but sometimes the idea is that Christians rule right now.
(Eph 2:4-7 ESV) 4 But God, being rich in mercy, because of the great love with which he loved us, 5 even when we were dead in our trespasses, made us alive together with Christ–by grace you have been saved– 6 and raised us up with him and seated us with him in the heavenly places in Christ Jesus, 7 so that in the coming ages he might show the immeasurable riches of his grace in kindness toward us in Christ Jesus.
In some sense, Christians are already in heaven, seated on the throne of Christ, reigning. Of course, there’s also an easier-to-understand sense in which we don’t yet reign. We live in the in-between times. But we do reign because we’ve been included in Christ who reigns. If we are “in Christ,” then we are in him as he sits on his throne and rule as part of him.
(Rom 5:17 ESV) For if, because of one man’s trespass, death reigned through that one man, much more will those who receive the abundance of grace and the free gift of righteousness reign in life through the one man Jesus Christ.
Most commentators take “reign in life” to refer to reigning in the next age, but the reign of death was defeated by Jesus at the resurrection. Therefore, Moo concludes,
Because Paul uses a future verb to depict the reigning of those who receive the gift, most think that the reference must be to the eschatological future. But, without denying that this is involved, and may even be the primary emphasis, it may be that this “reigning in life” begins with the reception of the gift of righteousness.
 The future tense may be, in other words, something of a “logical” future; future not so much in time as Paul writes but future from the standpoint of the reign of death in Adam (Murray).
Douglas J. Moo, The Epistle to the Romans, The New International Commentary on the New Testament, (Grand Rapids, MI: Wm. B. Eerdmans Publishing Co., 1996), 340.
This phrase may be interpreted with regard either to this life or to the coming one; NLT includes both (cf. 8:2).
Roger Mohrlang, Gerald L. Borchert, Cornerstone Biblical Commentary, Vol 14: Romans and Galatians, (Carol Stream, IL: Tyndale House Publishers, 2007), 95.
The doctrine of Christians reigning is taken from —
(Gen 1:26-28 ESV) 6 Then God said, “Let us make man in our image, after our likeness. And let them have dominion over the fish of the sea and over the birds of the heavens and over the livestock and over all the earth and over every creeping thing that creeps on the earth.” 27 So God created man in his own image, in the image of God he created him; male and female he created them. 28 And God blessed them. And God said to them, “Be fruitful and multiply and fill the earth and subdue it and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth.”
Have dominion is radah, the same word used for the reign of kings and of God himself. Man was created in God’s image to reign, and so restoration of man to God’s image necessarily implies a restoration to his rightful reign.
The Genesis account is echoed in the Psalms –
(Psa 8:3-9 ESV) 3 When I look at your heavens, the work of your fingers, the moon and the stars, which you have set in place, 4 what is man that you are mindful of him, and the son of man that you care for him? 5 Yet you have made him a little lower than the heavenly beings and crowned him with glory and honor. 6 You have given him dominion over the works of your hands; you have put all things under his feet, 7 all sheep and oxen, and also the beasts of the field, 8 the birds of the heavens, and the fish of the sea, whatever passes along the paths of the seas. 9 O LORD, our Lord, how majestic is your name in all the earth!
The Psalmist sees us as already having dominion over the creation.
(Dan 7:1 ESV) 18 But the saints of the Most High shall receive the kingdom and possess the kingdom forever, forever and ever.’
(Dan 7:21-22 ESV) 21 As I looked, this horn made war with the saints and prevailed over them, 22 until the Ancient of Days came, and judgment was given for the saints of the Most High, and the time came when the saints possessed the kingdom.
(Dan 7:1 ESV) 27 And the kingdom and the dominion and the greatness of the kingdoms under the whole heaven shall be given to the people of the saints of the Most High; their kingdom shall be an everlasting kingdom, and all dominions shall serve and obey them.’
Daniel is not easily interpreted, but there’s clearly the idea here that the saints will possess a kingdom and that all others will serve and obey them. In those days, kings were judges — the supreme court of the land — and so giving judgment to the saints puts them in the place of kings. It’s hard not to read this as a prediction of the rule of God’s saints.
With these verses in mind, we can see how the Revelator can say that those who’ve resisted Rome reign even today. (We’ll get to why I say this is about today.) The irony implicit in the teaching is that, even though Rome is persecuting and martyring the faithful, it’s actually the faithful who rule!