91 Then the fifth angel blew his trumpet, and I saw a star that had fallen to earth from the sky, and he was given the key to the shaft of the bottomless pit. 2 When he opened it, smoke poured out as though from a huge furnace, and the sunlight and air turned dark from the smoke. 3 Then locusts came from the smoke and descended on the earth, and they were given power to sting like scorpions. 4 They were told not to harm the grass or plants or trees, but only the people who did not have the seal of God on their foreheads. 5 They were told not to kill them but to torture them for five months with pain like the pain of a scorpion sting. 6 In those days people will seek death but will not find it. They will long to die, but death will flee from them! 7 The locusts looked like horses prepared for battle. They had what looked like gold crowns on their heads, and their faces looked like human faces. 8 They had hair like women's hair and teeth like the teeth of a lion. 9 They wore armor made of iron, and their wings roared like an army of chariots rushing into battle. 10 They had tails that stung like scorpions, and for five months they had the power to torment people.
Matthew Henry's Commentary on Revelation 9:1-10
Commentary on Revelation 9:1-12
(Read Revelation 9:1-12)
Upon sounding the fifth trumpet, a star fell from heaven to the earth. Having ceased to be a minister of Christ, he who is represented by this star becomes the minister of the devil; and lets loose the powers of hell against the churches of Christ. On the opening of the bottomless pit, there arose a great smoke. The devil carries on his designs by blinding the eyes of men, by putting out light and knowledge, and promoting ignorance and error. Out of this smoke there came a swarm of locusts, emblems of the devil's agents, who promote superstition, idolatry, error, and cruelty. The trees and the grass, the true believers, whether young or more advanced, should be untouched. But a secret poison and infection in the soul, should rob many others of purity, and afterwards of peace. The locusts had no power to hurt those who had the seal of God. God's all-powerful, distinguishing grace will keep his people from total and final apostacy. The power is limited to a short season; but it would be very sharp. In such events the faithful share the common calamity, but from the pestilence of error they might and would be safe. We collect from Scripture, that such errors were to try and prove the Christians, 1 Corinthians 11:19. And early writers plainly refer this to the first great host of corrupters who overspread the Christian church.