'The first resurrection,' mentioned in Revelation 20:5, 6, does not mean a first resurrection, but the essence and primary part of resurrection, which is salvation and eternal life. There is only one resurrection to life. A second does not happen, and is not mentioned anywhere in the Bible.

(References: Apocalypse Explained 6; Apocalypse Revealed 851; Revelation 20:5-6)

851. This is the first resurrection. This symbolically means that salvation and eternal life consist primarily in worshiping the Lord and living according to His commandments in the Word, because these are the means to conjunction with the Lord and affiliation with angels in heaven.

All of this is symbolized by the declaration, "This is the first resurrection," because it follows as a conclusion from the preceding declarations and so embraces them. The preceding ones that these words embrace are contained in verse 4, and partly also in verse 5. The declarations contained in verse 4 are the following:

I saw the souls of those who had been beheaded for the testimony of Jesus and for the Word of God, who had not worshiped the beast or its image, and had not received its mark on their foreheads or on their hands. And they lived and reigned with Christ... (Revelation 20:4)

The souls of those who had been beheaded for the testimony of Jesus and for the Word of God symbolize people who had been rejected by those caught up in falsities hatched out of their own intelligence, because they worshiped the Lord and lived in accordance with His commandments in the Word, as may be seen in nos. 846 and 847 above. Their not worshiping the beast or its image, and not receiving its mark on their foreheads and hands, means symbolically that they rejected the heretical doctrine of faith alone, as may be seen in no. 848 above. And their living and reigning with Christ for a thousand years means symbolically that they were conjoined with the Lord and affiliated with angels in heaven, as may be seen in no. 849 above. This, then, is what is involved in the declaration, "This is the first resurrection."

Resurrection symbolizes salvation and eternal life, and the first resurrection does not mean a first resurrection but the primary and essential implication of resurrection, thus salvation and eternal life. For there is but one resurrection to life. There is no second one. Consequently nowhere is a second resurrection mentioned. For once conjoined with the Lord, people remain conjoined with Him to eternity, and this in heaven. As the Lord says,

I am the resurrection and the life. Whoever believes in Me, though he die, shall live. Everyone who lives and believes in Me shall not die to eternity. (John 11:25-26)

That this is what is meant by the first resurrection is plain also from the verse that follows now.