Rev 11:5

5 If anyone desires to harm them, fire proceeds out of their mouth and devours their enemies. If anyone desires to harm them, he must be killed in this way. 

fire comes out of their mouths – to preach the truth, and to protest. They speak the word of God, “is not My word as fire” (Jer 23:29). The “fire” of course was the protest against the Nations, the Gentiles described in Rev 11:2.

Daniel described the fiery stream that issued from before the Almighty, and said, “the court shall be seated and they shall take away his dominion, to consume and destroy it forever.”

The beast had completely distorted the Gospel of Jesus Christ. By the time of the Reformation, the Church was selling the forgiveness of sins by way of “indulgences.” Indulgences were a payment to the Church in exchange for relief from purgatory, the place of suffering that the Church taught was necessary to endure, after death, before entering heaven. 

Jan Huss preached against indulgences more than 100 years, before Martin Luther attacked them in his famous 95 theses, in October of 1517.

The dark ages, from the 5th to 15th Century are so called because of the suppression of personal thought by the Church. Church inquisitions, and the burning of the writings of heretics make it difficult to understand the depth of opposition to the Church in these years. 

John Wycliffe, who died in 1384, translated the Bible into English and preached that the Bible should be the authority. He also said the claims of the papacy were unhistorical, and claimed that the moral depravity of the priests invalidated their sacraments.

If anyone wants to harm them, he must be killed in this way – by the word of God, which will devour him; “I am making My words in your mouth fire, and this people wood, it will consume them” (Jer 5:14).