Revelation 9:9

And they had breastplates, as it were breastplates of iron,
&c.] Alluding to the hard skin of the locusts, with which nature has fenced it ^F17; see ( Joel 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 many privileges they are possessed of, the laws made in their favour, and for their security; their breastplates were not breastplates of righteousness, faith, and love, nor in defence of truth, but against it. And some think the iron colour may denote the colour of their habit, their black garments:

and the sound of their wings was as the sound of chariots of many
horses running to battle;
see ( Joel 2:5 ) . The sound of locusts, when they fly or march in large companies, is very great. Pliny says ^F18, they make such a noise with their wings, when they fly, that they have been thought to have been other winged creatures; hence a locust, in Hebrew, is sometimes called (lulu) , the same name that is given to the high sounding cymbal. The sound of them is said to have been heard six miles ^F19. Aristotle ^F20 ascribes it to the rubbing of their legs or thighs one against another; and so the Ethiopic version here renders it, "the sound of their feet": this may be expressive of the swift and rapid incursions of the Saracens, and of the dreadful alarms to the nations which their invasions made; and may be applied to the noisy declamations, anathemas, excommunications, and interdicts of the Romish clergy.