The first resurrection that we read of in 1 Cor. 15 and Rev. 20 does not describe a period of time, but a class of persons having this characteristic name.
There are three divisions in verse 4 of Rev. 20.
1. “I saw thrones, and they sat upon them, and judgment was given unto them.”
2. “And... the souls of them that were beheaded for the witness of Jesus, and for the word of God.”
3. “And those which had not worshiped the beast, neither his image, neither had received his mark upon their foreheads, or in their hands.”
The first division includes all who are taken up at the rapture and they reign with Christ. He sees not only thrones but those who sit upon them. They share in the reign of Christ. (B)
The second class are those that are slain under the fifth seal. (See chapter 6:9-11.) (C)
The third class are the martyrs victorious over the full power of the beast. (See chapter 15:2.) (C)
The second and third classes who seem to have lost the earthly blessings of the kingdom by death, are specially named as having gained by death and resurrection, a place in the heavenly glory with those who reign with Christ. The first of these divisions, the sitters on the thrones, have been raised or changed at the rapture. The last two are said to be in company with them, "to live and reign with Christ a thousand years." All are named "The first resurrection.”
From Words of Truth