Verse 13. - 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").

9:13-21 The sixth angel sounded, and here the power of the Turks seems the subject. Their time is limited. They not only slew in war, but brought a poisonous and ruinous religion. The antichristian generation repented not under these dreadful judgments. From this sixth trumpet learn that God can make one enemy of the church a scourge and a plague to another. The idolatry in the remains of the eastern church and elsewhere, and the sins of professed Christians, render this prophecy and its fulfilment more wonderful. And the attentive reader of Scripture and history, may find his faith and hope strengthened by events, which in other respects fill his heart with anguish and his eyes with tears, while he sees that men who escape these plagues, repent not of their evil works, but go on with idolatries, wickedness, and cruelty, till wrath comes upon them to the utmost.And the sixth angel sounded,.... His trumpet:

and I heard a voice from the four horns of the golden altar, which is before God; the allusion is not to the altar of burnt offering, which was covered with brass, but to the altar of incense covered with gold; and hence here, and elsewhere, it is called "the golden altar", and was a figure of the intercession of Christ; for on this altar incense was offered, which was typical of the prayers of the saints offered by Christ, through his mediation: the matter of this altar was shittim wood, a wood that is incorruptible, and of long duration, denoting the perpetuity of Christ's intercession; and its being covered with gold expresses the glory and excellency of it; its form was foursquare, as is the city of the new Jerusalem, and shows that Christ's intercession avails for all his people in the four parts of the world: and on it were "four horns", which some think represent the four evangelists, or the Gospel sent into the four parts of the world, and which is the power of God unto salvation; and for the contempt of which, in the eastern empire, the judgments signified under this trumpet came upon it; though rather these may point at the large extent and fulness of Christ's intercession, for all his people, in the four corners of the earth, as well as his power to protect and defend them, and to scatter and destroy his and their enemies. This altar is said to be "before God", in a visionary way, as the altar of incense was before the vail, and the mercy seat, and by the ark of the testimony, Exodus 30:1; suggesting that Christ continually appears in the presence of God for all the saints. Now from hence was a "voice heard" by John, and which seems to be the voice of Christ, the advocate and intercessor. In the Greek text it is, "one voice"; not the voice of many angels round about the throne, nor of the souls under the altar, but of the one and only Mediator between God and man, the Lord Jesus Christ; and this was a voice, not supplicating, but commanding, being addressed to one of his ministering spirits.