3 Then from the smoke came locusts on the earth, and they were given power like the power of scorpions of the earth; 4 they were told not to harm the grass of the earth or any green growth or any tree, but only those of mankind who have not the seal of God upon their foreheads; 5 they were allowed to torture them for five months, but not to kill them, and their torture was like the torture of a scorpion, when it stings a man. 6 And in those days men will seek death and will not find it; they will long to die, and death will fly from them. 7 In appearance the locusts were like horses arrayed for battle; on their heads were what looked like crowns of gold; their faces were like human faces, 8 their hair like women's hair, and their teeth like lions' teeth; 9 they had scales like iron breastplates, and the noise of their wings was like the noise of many chariots with horses rushing into battle. 10 They have tails like scorpions, and stings, and their power of hurting men for five months lies in their tails. 11 They have as king over them the angel of the bottomless pit; his name in Hebrew is Abad'don, and in Greek he is called Apol'lyon.
Matthew Henry's Commentary on Revelation 9:3-11
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.