John the Apostle
Revelation 9:9BSB·traditional attribution

They also had breastplates like breastplates of iron, and the sound of their wings was like the roar of many horses and chariots rushing into battle.

Matthew Henry Presbyterian @wholebiblehenry

Upon the sounding of this trumpet, the things to be observed are, 1. A star falling from heaven to the earth. Some think this star represents some eminent bishop in the Christian church, some angel of the church; for, in the same way of speaking by which pastors are called stars, the church is called heaven; but who this is expositors do not agree.

Commenting on Revelation 9:1-12

John Gill Reformed Baptist @doctorgill

And they had breastplates, as it were breastplates of iron,.... Alluding to the hard skin of the locusts, with which nature has fenced it (q); see Joe 2:8; and denotes the armour with which the Saracens were accoutred: and if to be understood of the western locusts, the hardness of their hearts, their seared consciences, or their protection by the princes of the earth, the...

Albert Barnes Presbyterian @notesbybarnes

Verse 9. And they had breastplates, as it were breastplates of iron. Hard, horny, impenetrable, as if they were made of iron. The locust has a firm and hard cuticle on the forepart of the breast, which serves for a shield or defence while it moves in the thorny and furzy vegetation.