And I will appoint my two witnesses, and they will prophesy for 1,260 days, clothed in sackcloth.” 4 They are “the two olive trees” and the two lampstands, and “they stand before the Lord of the earth.”[a]5 If anyone tries to harm them, fire comes from their mouths and devours their enemies. This is how anyone who wants to harm them must die. 6 They have power to shut up the heavens so that it will not rain during the time they are prophesying; and they have power to turn the waters into blood and to strike the earth with every kind of plague as often as they want. (Revelation 11:3-6)
During the tribulation period God will temporarily give control of most of the Earth to the Antichrist and his satanicly inspired followers. He will allow the Antichrist to capture and kill most Christians on Earth (Revelation 13:17). He will allow the Antichrist and his army of unbelieving Gentiles to defeat Israel and occupy Jerusalem.
However, God will send two witnesses to remind the forces of the Antichrist that they have no power except what has been temporarily allowed them by God. These two witnesses will appear “clothed in sackcloth” to remind all observers to repent before God’s judgment. They will have supernatural power to kill anyone who opposes them, in broad daylight. They will also have the power to make the rain stop, and they will send out other plagues as well. Their power appears to extend over the entire Earth. Thus they will reveal how powerless the Antichrist is, despite his military victories.
Their ministry will be for the 1,260 days (three and a half years) that the unbelieving Gentiles control Jerusalem. During the same time God will protect the Israeli survivors in a nearby wilderness refuge (Revelation 12:14).