Revelation 9:17

“And thus I saw the horses in the vision, and them that sat on them, etc.] In such numbers, and with horsemen on them, and in such order, and in appearance, as follows: having breastplates of fire, and of jacinth and brimstone; which may be understood either literally of their external breastplates, which being of polished iron, according to the custom of these people, looked at a distance like sparkling fire, and seemed to be of the colour of hyacinth, or of a sky colour, and appeared as flaming sulphur; though some think that their breastplates were of different colours, some looked like fire, others like jacinth, and others like brimstone; or it may denote that they would be accoutred in…”

“thus--as follows. of fire--the fiery color of the breastplates answering to the fire which issued out of their mouths. of jacinth--literally, "of hyacinth color," the hyacinth of the ancients answering to our dark blue iris: thus, their dark, dull-colored breastplates correspond to the smoke out of their mouths. brimstone--sulphur-colored: answering to the brimstone or sulphur out of their mouths.”

“And thus I saw the horses in the vision - That is, he saw them as he proceeds to describe them, for the word “thus” - οὕτως houtōs - refers to what follows. Compare Robinson’s Lexicon on the word (b), and see Matthew 1:18; Matthew 2:5; John 21:1; Hebrews 4:4. Prof. Stuart, however, refers to what precedes. The meaning, as it seems to me, is, that he fixed his attention on the appearance of the immense army - the horses and their riders, and proceeded to describe them as they struck him. And them that sat on them - He fixed the attention on horse and rider. Their appearance was unusual, and deserved a particular description. Having breastplates of fire - That is, those who sat on them had…”

“9:17-19 The riders had armor in colors that matched the plagues of their horses, with red for fire, blue for smoke, and yellow for sulfur—all of which are signs of judgment in Scripture (see 14:10-11; 19:20; Gen 19:24-28; Ps 11:6; Ezek 38:22; Luke 17:29). • The horses are reminiscent of the terrifying monsters of Greek tales pictured on ancient buildings and celebrated in ancient dramas. • One-third: See study note on Rev 8:7-12.”

“having: This appears to point out the scarlet, blue and yellow colours, for which the Turks have always been remarkable. The "four angels bound in the Euphrates" denote their four sultanies bordering on that river, where they were confined till after the period of the Crusades. The time for which they were prepared, "an hour, and a day, and a month, and a year," computing a year for each day, amounts to 391 years, 15 days; and from their first conquest over the Christians, ad 1281, to the taking of Cameniec from the Poles, ad 1672, which was the last conquest by which their dominion was extended, is exactly that period. Rev 9:9 jacinth: Rev 21:20 brimstone: Rev 9:18, Rev 14:10, Rev 19:20,…”