"The fifth angel sounded his shofar; and I saw a star that had fallen out of heaven onto the earth, and he was given the key to the shaft leading down to the Abyss. He opened the shaft of the Abyss, and there went up smoke from the shaft like the smoke of a huge furnace; the sun was darkened, and the sky too, by the smoke from the shaft. Then out of the smoke onto the earth came locusts, and they were given power like the power scorpions have on earth. They were instructed not to harm the grass on the earth, any green plant or any tree, but only the people who did not have the seal of God on their foreheads. The locusts were not allowed to kill them, only to inflict pain on them for five months; and the pain they caused was like the pain of a scorpion sting. In those days people will seek death but will not find it; they will long to die, but death will elude them. Now these locusts looked like horses outfitted for battle. On their heads were what looked like crowns of gold, and their faces were like human faces. They had hair like women's hair, and their teeth were like those of lions. Their chests were like iron breastplates, and the sound their wings made was like the roar of many horses and chariots rushing into battle. They had tails like those of scorpions, with stings; and in their tails was their power to hurt people for five months. " Revelation 9:1-10 (CJB)
The seal of G-D referred to in Revelation 9 is the blood of Yeshua Ha'Mashiach. It will not be seen in the natural world. We can only see things in the natural world. This seal will only be visible in the unseen world! The blood of Yeshua Ha'Mashiach will be visible to the locusts so that they can "passover" the "wheat", those who have accepted Yeshua as their Mashiach (Messiah)! These souls on the earth are protected by the blood of the Lamb. This is similar to what happened in Egypt when death fell over the land of Egypt.
"For that night, I will pass through the land of Egypt and kill all the firstborn in the land of Egypt, both men and animals. I will execute judgment against all the gods of Egypt. I am ADONAI. The blood will serve you as a sign marking the houses where you are. When I see the blood, I will pass over [Hebrew: pasach] you. When I strike the land of Egypt, the death blow will not strike you." Sh'mot (Exodus) 12:12-13 (CJB)
Notice that the Holy One of Isra'el tells Moshe and Aarhon to instruct the house of Isra'el living in Egypt to take a male sheep or a goat without blemish and to slaughter it at dusk and to place the blood of this animal on the two sides and top of their door frame. Even in Sh'mot, the Holy One of Isra'el was giving a clandestine message of how He would save humanity through the blood of HIS only begotten Son, Yeshua, who shed HIS blood as an atonement for the sins of humanity.
"'ADONAI spoke to Moshe and Aharon in the land of Egypt. He said, "You are to begin your calendar with this month. It will be the first month of the year for you. Speak to all the assembly of Isra'el and say, 'On the tenth day of this month, each man is to take a lamb or kid for his family, one per household, except that if the household is too small for a whole lamb or kid, then he and his next-door neighbor should share one, dividing it in proportion to the number of people eating it. Your animal must be without defect, a male in its first year, and you may choose it from either the sheep or the goats. "You are to keep it until the fourteenth day of the month, and then the entire assembly of the community of Isra'el will slaughter it at dusk. They are to take some of the blood and smear it on the two sides and top of the door-frame at the entrance of the house in which they eat it.'" Exodus (Sh'mot) 12:1-7 (CJB)
Now, we see in Revelation 9, YAH seals the redeemed of the Lord with the blood of Yeshua to protect His children from the judgment that will fall on the earth for disobedience. Glory! HalleluYAH!
Only human beings without the seal of G-D on their forehead, which again will be invisible to humanity, will suffer the infliction of great pain for five months by these locusts. These locusts will be in the unseen world, but their effect will cause pain like the pain of a scorpion sting. Remember, that there is a seen world and a unseen world. We, as human beings, can only see what is in the seen or physical world. We cannot see things in the spirit world even though many things in the spirit world affect us. We cannot see demonic forces that influence evil actions. We cannot see angels that protect people from danger. In the same manner, many things that are written in the book of Revelation will not be seen in the physical world. However, their effect will be experienced by the children of disobedience.
Those of you who do not know Yeshua, please come to Him today so that you may receive the seal of G-D and not endure these plagues and torments written about in the book of Revelation. Accept Yeshua as your Savior so that you may have eternal life and are blessed to be invited to the wedding feast of the Lamb!
"'Let us rejoice and be glad! Let us give him the glory! For the time has come for the wedding of the Lamb! His Bride has prepared herself with fine linen, bright and clean has been given her to wear. "Fine linen" means the righteous deeds of God's people. The angel said to me, "Write: 'How blessed are those who have been invited to the wedding feast of the Lamb!'" Then he added, "These are God's very words." Revelation 19:7-9 (CJB)