John saw the thrones of the martyrs who lived again and had authority to judge people. Those martyrs are the first people whom God will cause to live again. They will reign with Christ during the 1,000 years.

Revelation 20:4-6

4 I saw thrones on which people were sitting. They were given {God gave those people} authority to judge other people. I also saw the souls of people whose heads had been {whose heads others had} cut off because of their telling people about Jesus and declaring God’s message. They were people who refused to worship the beast or its image, and who did not allow the beast’s agents to put the beast’s mark on them, either on their foreheads or on their hands. They became alive again, and they ruled with Christ during those 1,000 years. 5 They were the ones who lived again the first time that God caused dead people to live again. The rest of the believers who had died did not live again until after those 1,000 years. 6 ◄God will be pleased with/How happy will be► those who live again that first time. God will consider them holy. They will not die [PRS] a second time. Instead, they will be priests who serve God and Christ, and they will rule with Christ during those 1,000 years.