9:1 It is not known whether this “star” that fell “from heaven” is Satan, a fallen angel, Christ, or a good angel. Most likely it is a good angel, because the key to the shaft of the bottomless pit is normally held by Christ (1:17, 18), and it was temporarily given to this other being from heaven (see also 20:1). This being, whoever he may be, is still under God’s control and authority. The bottomless pit represents the place of the demons and of Satan, the king of demons (9:11). See also Luke 8:31 for another reference to the bottomless pit.
9:3 The prophet Joel described a locust plague as a foreshadowing of the “day of the Lord,” meaning God’s coming judgment (Joel 2:1-10). In the Old Testament, locusts were symbols of destruction because they destroyed vegetation. Here, however, they symbolize an invasion of demons called to torture people who do not believe in God. The limitations placed on the demons (they could only torment people for five months) show that they are under God’s authority.
9:3ff Most likely these locusts are demons—evil spirits ruled by Satan who tempt people to sin. They were not created by Satan, because God is the Creator of all; rather, they are fallen angels who joined Satan in his rebellion. God limits what they can do; they can do nothing without his permission. Their main purpose on earth is to prevent, distort, or destroy people’s relationship with God. Because they are corrupt and degenerate, their appearance reflects the distortion of their spirits. While it is important to recognize their evil activity so we can stay away from them, we must avoid any curiosity about or involvement with demonic forces or with the occult.
9:11 The locust-demons have a leader whose name in Hebrew and in Greek means “Destroyer.” It may be a play on words by John to show that those who worshiped the great god Apollo worshiped only a demon.
9:13 The altar in the Temple had four projections, one at each corner, and these were called the horns of the altar (see Exodus 27:2).
9:14 The word angels here means fallen angels or demons. These four unidentified demons will be exceedingly evil and destructive. But note that they do not have the power to release themselves and do their evil work on earth. Instead, they are held back by God and will be released at a specific time, doing only what he allows them to do.
9:16 In John’s day, this number of mounted troops in an army was inconceivable, but today there are countries and alliances that could easily amass this many soldiers. This huge army, led by the four demons, will be sent out to destroy one-third of the earth’s population. But the judgment is still not complete.
9:20, 21 These people were so hard-hearted that even plagues did not drive them to God. People don’t usually fall into immorality and evil suddenly—they slip into it a little bit at a time until, hardly realizing what has happened, they are irrevocably mired in their wicked ways. Any person who allows sin to take root in his or her life will end up in this predicament. Temptation entertained today becomes sin tomorrow, a habit the next day, then death and separation from God forever (see James 1:15). To think you could never become this evil is the first step toward a hard heart. Acknowledge your need to confess your sin before God.