John the Apostle
Revelation 9:13ESV·traditional attribution

Then the sixth angel blew his trumpet, and I heard a voice from the four horns of the golden altar before God,

Matthew Henry Presbyterian @wholebiblehenry

Here let us consider the preface to this vision, and then the vision itself. I. The preface to this vision: A voice was heard from the horns of the golden altar, Rev 9:13, Rev 9:14. Here observe, 1. The power of the church's enemies is restrained till God gives the word to have them turned loose. 2.

Commenting on Revelation 9:13-21

John Gill Reformed Baptist @doctorgill

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...

Albert Barnes Presbyterian @notesbybarnes

Verse 13. And the sixth angel sounded. , seq. And I heard a voice from the four horns of the golden altar which is before God. In the language here used there is an allusion to the temple, but the scene is evidently laid in heaven.