And the sixth angel sounded, and I heard a voice; I heard one voice, perhaps in contradistinction to the four horns next mentioned. From the four horns of the golden altar which is before God; the golden altar before God.
The balance of authority seems in favour of retaining τεσσάρων, "four," although the Revisers omit it. It is inserted in B, P, Andreas, Arethas, Primasius, etc., but emitted in א A, Syriac, Coptic, Bede, etc.
Many commentators (eg. Vitringa, Hengstenberg) lay special stress upon it; and some represent the horns as the four Gospels, which speak with one voice. The voice issues from the altar, as in Revelation 6:10; Revelation 16:7.
The voice, issuing from the resting place of the souls of the martyrs, denounces the impending woe. The altar is the golden altar of incense (Revelation 8:3) which is before (the throne of) God, and which, in the earthly temple, stood before the veil (Exodus 40:26).
This altar had four "horns" projecting at the corners (Exodus 30:2; see also Smith's 'Dictionary of the Bible,' art. "Altar").