Poole on Revelation 5:10: The Royal Priesthood
Verse 10: (Ex. 19:6; 1 Pet. 2:5, 9; Rev. 1:6; 20:6; 22:5) And hast made us unto our God kings and priests: and we shall reign on the earth.
[Thou hast made us, ἡμᾶς] In the Complutensian Codex and another [which Codices Grotius follows] it is αὐτοὺς/them, namely, the saints that are yet in the earth. The speech passes from the first person plural to the third person, not unhappily: for they speak both concerning themselves and concerning others (Grotius).
[A kingdom, etc.] Thus also a manuscript, βασιλείαν/kingdom, an abstraction in the place of a concrete, after the fashion of the Hebrews: like ἱεράτευμα/priesthood in 1 Peter 2:5, 9 (Grotius).
[Βασιλεῖς, etc.] See what things were said on Revelation 1:6 (Menochius). Kings and Priests (Erasmus, Piscator, Beza, etc.). In a certain sense even in this life (Grotius).
[And we shall reign upon the earth] Either, 1. that new one promised, Matthew 5:5 (Andreas Cæsarius in Pareus); 2 Peter 3:13 (Estius): or, 2. that Earth in which mortals act (Menochius, similarly Pareus); but not with secular power (Pareus), but rather with a spiritual scepter (Pareus, similarly Durham, Cluverus), just as Christ also reigns here, with whom the faithful also reign (Pareus). Who here reign, either, 1. by the kingdom of grace (Gomar, Forbes), through the first resurrection (Cluverus), by subjugating carnal desires (Pareus, similarly Cluverus, Durham). The sense: Not only in the heavens in the future shall we reign and be liberated from sin, but also in the earth, where sin shall not have dominion over us, Romans 6:14 (Durham). Or, 2. by the kingdom of glory, or, in the day of judgment (Gomar), when the saints will judge the world with Christ, 1 Corinthians 6:2 (Pareus). They shall reign also when all kingdoms shall be made God’s and Christ’s, Revelation 11:15 compared with Daniel 7:27 (Cocceius). Καὶ βασιλεύσομεν, and we shall reign, is here in place of ἵνα βασιλεύωμεν, that we might reign, so that it might properly be speech concerning the Apostles and Presbyters, to whom the government of the Churches was given. See Revelation 2:27; 4:4. And this heavenly Kingdom is in the earth: for what they bind on earth is bound in heaven, Matthew 18:18 (Grotius). In the Complutensian Codex and another, it is καὶ βασιλεύσουσιν, and they shall reign (Beza). Others: καὶ βασιλεύουσιν, and they reign, in the place of ἵνα βασιλεύωμεν, that we might reign (Grotius).
And hast made us, etc.: The four living creatures and four and twenty elders (by which are represented the ministers and members of the church of Christ) go on in showing why they had reason to proclaim Christ worthy to be the Prophet to his church, to open the counsels of God to them, namely, because of the great love he had showed to them, not only in redeeming them with his blood from the guilt and power of sin, but in making them kings and priests; giving them the same privileges that the Jewish church had, who were called a royal priesthood, Exodus 19:6; giving them a power (as priests) to offer up (not such bloody fleshly sacrifices as they offered, but) spiritual sacrifices, acceptable to God through the Beloved, 1 Peter 2:5: and also (as kings) to rule over their lusts and sensitive appetite; and to reign hereafter on the earth, judging the world (1 Corinthians 6:3) at the great day, with the great Judge of the quick and the dead.
 Greek: καὶ ἐποίησας ἡμᾶς τῷ Θεῷ ἡμῶν βασιλεῖς καὶ ἱερεῖς, καὶ βασιλεύσομεν ἐπὶ τῆς γῆς.  Thus Codices Alexandrinus and Sinaiticus, and the great majority of Byzantine manuscripts.  Codex Alexandrinus.  Codex Alexandrinus and a number of Byzantine manuscripts read βασιλεύουσιν, they reign. Codex Sinaiticus and a number of Byzantine manuscripts read βασιλεύσουσιν, they shall reign.