John the Apostle
Revelation 9:14BSB·traditional attribution

saying to the sixth angel with the trumpet, “Release the four angels who are bound at the great river Euphrates.”

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

Saying to the sixth angel which had the trumpet,.... The sixth trumpet, which was given him, and he had prepared himself to sound, and had sounded: loose the four angels which are bound in the great river Euphrates; not the four angels in Rev 7:1; they stood upon the four corners of the earth; these were in, or at the river Euphrates; they held the...

Albert Barnes Presbyterian @notesbybarnes

Verse 14. Saying to the sixth angel, which had the trumpet. . Loose, etc. This power, it would seem, was given to the sixth angel in addition to his office of blowing the trumpet. All this, of course, was in vision, and cannot be literally interpreted.