A.T. Robertson Commentary Revelation 12:10

"And I heard a great voice in heaven, saying, Now is come the salvation, and the power, and the kingdom of our God, and the authority of his Christ: for the accuser of our brethren is cast down, who accuseth them before our God day and night." — Revelation 12:10 (ASV)

A great voice saying (φωνην μεγαλην λεγουσαν). Accusative after ηκουσα in this phrase as in 5:11; 10:4; 14:2; 18:4, but the genitive φωνης λεγουσης in 11:12; 14:13. We are not told whence this voice or song comes, possibly from one of the twenty-four elders (Swete) or some other heavenly beings (11:15) who can sympathize with human beings (19:10), the martyrs in heaven (Charles).

Now is come (αρτ εγενετο). Αρτ (John 13:33) shows how recent the downfall of Satan here proleptically pictured as behind us in time (aorist tense εγενετο).

The salvation (η σωτηρια). Here "the victory" as in 7:10; 19:1.

The power (η δυναμις). Gods power over the dragon (cf. 7:12; 11:17; 19:1).

The kingdom (η βασιλεια). "The empire of God" as in 11:15.

The authority of his Christ (η εξουσια του Χριστου αυτου). Which Christ received from the Father (Matthew 28:18; John 17:2). See 11:15 (Psalms 2:2) for "his Anointed."

The accuser (ο κατηγωρ). The regular form, κατηγορος, occurs in Joh 8:10; Acts 23:30,35; 25:16,18 and in many MSS. here in Re 12:10, but A reads κατηγωρ, which Westcott and Hort accept. It was once considered a Greek transliteration of a Hebrew word, but Deissmann (Light, etc., p. 93f.) quotes it from a vernacular magical papyrus of the fourth century A.D. with no sign of Jewish or Christian influence, just as διακων appears as a vernacular form of διακονος. Only here is the word applied to Satan in the N.T. In late Judaism Satan is the accuser, and Michael the defender, of the faithful.

Of our brethren (των αδελφων ημων). The saints still on earth battling with Satan and his devices.

Which accuseth them (ο κατηγορων αυτους). Articular present active participle of κατηγορεω, old verb, to accuse, usually with the genitive of the person (John 5:45), but here with the accusative. This is the devil's constant occupation (Job 1:6f.).

Day and night (ημερας κα νυκτος). Genitive of time. "By day and by night."