“blessed and holy is the one having a share in the first resurrection, over these the second death does not have power, but they will be priests of God and of the Messiah and they will reign with Him a thousand years” μακάριος καὶ ἅγιος ὁ ἔχων μέρος ἐν τῇ ἀναστάσει τῇ πρώτῃ· ἐπὶ τούτων ὁ δεύτερος θάνατος οὐκ ἔχει ἐξουσίαν, ἀλλ᾽ ἔσονται ἱερεῖς τοῦ θεοῦ καὶ τοῦ Χριστοῦ καὶ βασιλεύσουσιν μετ᾽ αὐτοῦ [τὰ] χίλια ἔτη). Verse 6 is an interpretation of the first resurrection and constitutes the main point of verses 1-6. John’s assertion that the saints are blessed is grounded in three realities: the second death has no power over them, they will be priests of God and of Christ, and they will reign with Christ for a thousand years. This is the fifth of seven benedictions in the book of Revelation (1:3, 14:13, 16:15, 19:19, 20:6, 22:7, 22:14), and contains close parallels with 2:10-11 and 14:13.
Revelation 2:11 is contains the first reference to the “second death” in John’s apocalypse. In fact, the next time the phrase appears is in this verse, 20:6. In 2:10-11, Christ promises the church of Smyrna that if they are “faithful unto death,” He will give them, “the crown of life,” and that “The one who conquers will not be hurt by the second death.” In the context, conquering is closely tied to remaining faithful unto death. The church at Smyrna was facing persecution by Jews and Satan himself – but Christ’s call is that if they remain faithful even unto a martyr’s death, and so overcome the devil (cf. 12:11), they will receive the crown of life and reign with God. Similarly, John sees in Revelation 20 saints who were faithful unto death, who are sat on thrones, reign with Christ, and avoid the second death. Given the use of similar language elsewhere (James 1:12, Martyrdom of Polycarp 17:1, Hermas, Similitudes 8.3.6), as well as the fact that the crown is a reward for conquering/overcoming Satan by remaining faithful unto death, the crown is given to the saints at death. Therefore, Revelation 2:10-11 supports the amillennial view of the resurrection and reigning saints in Revelation 20 as being during the intermediate state in heaven.
The benediction in 14:13 further confirms this view. There the Heavenly voice tells John to write, “Blessed are the dead who died in the Lord from now on…they may rest from their labors, for their deeds follow them.” This verse itself, looks back on 6:11 where the disembodied saints are given white robes and told to “rest a little longer.” While these do not in and of themselves necessitate the amillennial view, they do provide further examples of how John’s apocalypse views the intermediate state as one of blessedness.
The clause ἔσονται ἱερεῖς τοῦ θεοῦ καὶ τοῦ Χριστοῦ is an allusion back to the promise
given to Israel in Exodus 19:6 and which is now applied to all the saints. John
has already used this language in 1:6 and 5:10 and portrays the saints in
heaven throughout his book as engaging in priestly activities (7:15, 14:1-5,
15:2-4, 22:3). This promise is already inaugurated (1 Peter 2:9) and will be
consummated in the New Heaven and New Earth (22:3).
 Beale, NIGTC, p. 244-245. This is also confirmed by the fact that the disembodied saints in 6:10 are given white robes, in fulfillment of Christ’s promise in 3:5.