A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
rev 9:1THE FIFTH TRUMPET: THE FALLEN STAR OPENS THE ABYSS WHENCE ISSUE LOCUSTS. THE SIXTH TRUMPET. FOUR ANGELS AT THE EUPHRATES LOOSED. (Rev. 9:1-21)
The last three trumpets of the seven are called, from Rev 8:13, the woe-trumpets.
fall--rather as Greek, "fallen." When John saw it, it was not in the act of falling, but had fallen already. This is a connecting link of this fifth trumpet with Rev 12:8-9, Rev 12:12, "Woe to the inhabiters of the earth, for the devil is come down," &c. Compare Isa 14:12, "How art thou fallen from heaven, Lucifer, son of the morning!"
the bottomless pit--Greek, "the pit of the abyss"; the orifice of the hell where Satan and his demons dwell.
rev 9:3upon--Greek, "unto," or "into."
as the scorpions of the earth--as contrasted with the "locusts" which come up from hell, and are not "of the earth."
have power--namely, to sting.
rev 9:4not hurt the grass . . . neither . . . green thing . . . neither . . . tree--the food on which they ordinarily prey. Therefore, not natural and ordinary locusts. Their natural instinct is supernaturally restrained to mark the judgment as altogether divine.
those men which--Greek, "the men whosoever."
in, &c.--Greek, "upon their forehead." Thus this fifth trumpet is proved to follow the sealing in Rev 7:1-8, under the sixth seal. None of the saints are hurt by these locusts, which is not true of the saints in Mohammed's attack, who is supposed by many to be meant by the locusts; for many true believers fell in the Mohammedan invasions of Christendom.
rev 9:5they . . . they--The subject changes: the first "they" is the locusts; the second is the unsealed.
five months--the ordinary time in the year during which locusts continue their ravages.
their torment--the torment of the sufferers. This fifth verse and Rev 9:6 cannot refer to an invading army. For an army would kill, and not merely torment.
rev 9:6shall desire--Greek, "eagerly desire"; set their mind on.
shall flee--So B, Vulgate, Syriac, and Coptic read. But A and Aleph read, "fleeth," namely continually. In Rev 6:16, which is at a later stage of God's judgments, the ungodly seek annihilation, not from the torment of their suffering, but from fear of the face of the Lamb before whom they have to stand.
rev 9:7prepared unto battle--Greek, "made ready unto war." Compare Note, see on Joe 2:4, where the resemblance of locusts to horses is traced: the plates of a horse armed for battle are an image on a larger scale of the outer shell of the locust.
crowns-- (Nah 3:17). ELLIOTT explains this of the turbans of Mohammedans. But how could turbans be "like gold?" ALFORD understands it of the head of the locusts actually ending in a crown-shaped fillet which resembled gold in its material.
as the faces of men--The "as" seems to imply the locusts here do not mean men. At the same time they are not natural locusts, for these do not sting men (Rev 9:5). They must be supernatural.
rev 9:8hair of women--long and flowing. An Arabic proverb compares the antlers of locusts to the hair of girls. EWALD in ALFORD understands the allusion to be to the hair on the legs or bodies of the locusts: compare "rough caterpillars," Jer 51:27.
as the teeth of lions-- (Joe 1:6, as to locusts).
rev 9:9as it were breastplates of iron--not such as forms the thorax of the natural locust.
as . . . chariots-- (Joe 2:5-7).
rev 9:10tails like unto scorpions--like unto the tails of scorpions.
and there were stings--There is no oldest manuscript for this reading. A, B, Aleph, Syriac, and Coptic read, "and (they have) stings: and in their tails (is) their power (literally, 'authority': authorized power) to hurt."
rev 9:11And--so Syriac. But A, B, and Aleph, omit "and."
a king . . . which is the angel--English Version, agreeing with A, Aleph, reads the (Greek) article before "angel," in which reading we must translate, "They have as king over them the angel," &c. Satan (compare Rev 9:1). Omitting the article with B, we must translate, "They have as king an angel," &c.: one of the chief demons under Satan: I prefer from Rev 9:1, the former.
bottomless pit--Greek, "abyss."
Abaddon--that is, perdition or destruction (Job 26:6; Pro 27:20). The locusts are supernatural instruments in the hands of Satan to torment, and yet not kill, the ungodly, under this fifth trumpet. Just as in the case of godly Job, Satan was allowed to torment with elephantiasis, but not to touch his life. In Rev 9:20, these two woe-trumpets are expressly called "plagues." ANDREAS OF CÃSAREA, A.D. 500, held, in his Commentary on Revelation, that the locusts mean evil spirits again permitted to come forth on earth and afflict men with various plagues.
rev 9:12Greek, "The one woe."
hereafter--Greek, "after these things." I agree with ALFORD and DE BURGH, that these locusts from the abyss refer to judgments about to fall on the ungodly immediately before Christ's second advent. None of the interpretations which regard them as past, are satisfactory. Joe 1:2-7; Joe 2:1-11, is strictly parallel and expressly refers (Joe 2:11) to THE DAY OF THE LORD GREAT AND VERY TERRIBLE: Joe 2:10 gives the portents accompanying the day of the Lord's coming, the earth quaking, the heavens trembling, the sun, moon, and stars, withdrawing their shining: Joe 2:18, Joe 2:31-32, also point to the immediately succeeding deliverance of Jerusalem: compare also, the previous last conflict in the valley of Jehoshaphat, and the dwelling of God thenceforth in Zion, blessing Judah. DE BURGH confines the locust judgment to the Israelite land, even as the sealed in Rev 7:1-8 are Israelites: not that there are not others sealed as elect in the earth; but that, the judgment being confined to Palestine, the sealed of Israel alone needed to be expressly excepted from the visitation. Therefore, he translates throughout, "the land" (that is, of Israel and Judah), instead of "the earth." I incline to agree with him.
rev 9:13a voice--literally, "one voice."
from--Greek, "out of."
the four horns--A, Vulgate (Amiatinus manuscript), Coptic, and Syriac omit "four." B and CYPRIAN support it. The four horns together gave forth their voice, not diverse, but one. God's revelation (for example, the Gospel), though in its aspects fourfold (four expressing world-wide extension: whence four is the number of the Evangelists), still has but one and the same voice. However, from the parallelism of this sixth trumpet to the fifth seal (Rev 6:9-10), the martyrs' cry for the avenging of their blood from the altar reaching its consummation under the sixth seal and sixth trumpet, I prefer understanding this cry from the four corners of the altar to refer to the saints' prayerful cry from the four quarters of the world, incensed by the angel, and ascending to God from the golden altar of incense, and bringing down in consequence fiery judgments. Aleph omits the whole clause, "one from the four horns."
rev 9:14in, &c.--Greek, "epi to potamo"; "on," or "at the great river."
Euphrates--(Compare Rev 16:12). The river whereat Babylon, the ancient foe of God's people was situated. Again, whether from the literal region of the Euphrates, or from the spiritual Babylon (the apostate Church, especially ROME), four angelic ministers of God's judgments shall go forth, assembling an army of horsemen throughout the four quarters of the earth, to slay a third of men, the brunt of the visitation shall be on Palestine.
rev 9:15were--"which had been prepared" [TREGELLES rightly].
for an hour, and a day, and a month, and a year--rather as Greek, "for (that is, against) THE hour, and day, and month, and year," namely, appointed by God. The Greek article (teen), put once only before all the periods, implies that the hour in the day, and the day in the month, and the month in the year, and the year itself, had been definitely fixed by God. The article would have been omitted had a sum-total of periods been specified, namely, three hundred ninety-one years and one month (the period from A.D. 1281, when the Turks first conquered the Christians, to 1672, their last conquest of them, since which last date their empire has declined).
slay--not merely to "hurt" (Rev 9:10), as in the fifth trumpet.
third part--(See on Rev 8:7-12).
of men--namely, of earthy men, Rev 8:13, "inhabiters of the earth," as distinguished from God's sealed people (of which the sealed of Israel, Rev 7:1-8, form the nucleus).
rev 9:16Compare with these two hundred million, Psa 68:17; Dan 7:10. The hosts here are evidently, from their numbers and their appearance (Rev 9:17), not merely human hosts, but probably infernal, though constrained to work out God's will (compare Rev 9:1-2).
and I heard--A, B, Aleph, Vulgate, Syriac, Coptic, and CYPRIAN omit "and."
rev 9:17thus--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.
rev 9:18By these three--A, B, C, and Aleph read (apo for kupo), "From"; implying the direction whence the slaughter came; not direct instrumentality as "by" implies. A, B, C, Aleph also add "plagues" after "three." English Version reading, which omits it, is not well supported.
by the fire--Greek, "owing to the fire," literally, "out of."
rev 9:19their--A, B, C and Aleph read, "the power of the horses."
in their mouth--whence issued the fire, smoke, and brimstone (Rev 9:17). Many interpreters understand the horsemen to refer to the myriads of Turkish cavalry arrayed in scarlet, blue, and yellow (fire, hyacinth, and brimstone), the lion-headed horses denoting their invincible courage, and the fire and brimstone out of their mouths, the gunpowder and artillery introduced into Europe about this time, and employed by the Turks; the tails, like serpents, having a venomous sting, the false religion of Mohammed supplanting Christianity, or, as ELLIOTT thinks, the Turkish pachas' horse tails, worn as a symbol of authority. (!) All this is very doubtful. Considering the parallelism of this sixth trumpet to the sixth seal, the likelihood is that events are intended immediately preceding the Lord's coming. "The false prophet" (as Isa 9:15 proves), or second beast, having the horns of a lamb, but speaking as the dragon, who supports by lying miracles the final Antichrist, seems to me to be intended. Mohammed, doubtless, is a forerunner of him, but not the exhaustive fulfiller of the prophecy here: Satan will, probably, towards the end, bring out all the powers of hell for the last conflict (see on Rev 9:20, on "devils"; compare Rev 9:1-2, Rev 9:17-18).
with them--with the serpent heads and their venomous fangs.
rev 9:20the rest of the men--that is, the ungodly.
yet--So A, Vulgate, Syriac, and Coptic. B and Aleph read, "did not even repent of," namely, so as to give up "the works," &c. Like Pharaoh hardening his heart against repentance notwithstanding the plagues.
of their hands-- (Deu 31:29). Especially the idols made by their hands. Compare Rev 13:14-15, "the image of the beast" Rev 19:20.
that they should not--So B reads. But A, C, and Aleph read "that they shall not": implying a prophecy of certainty that it shall be so.
devils--Greek, "demons" which lurk beneath the idols which idolaters worship.
rev 9:21sorceries--witchcrafts by means of drugs (so the Greek). One of the fruits of the unrenewed flesh: the sin of the heathen: about to be repeated by apostate Christians in the last days, Rev 22:15, "sorcerers." The heathen who shall have rejected the proffered Gospel and clung to their fleshly lusts, and apostate Christians who shall have relapsed into the same shall share the same terrible judgments. The worship of images was established in the East in A.D. 842.
fornication--singular: whereas the other sins are in the plural. Other sins are perpetrated at intervals: those lacking purity of heart indulge in one perpetual fornication [BENGEL].