Revelation 12:15
And the serpent cast out of his mouth water as a flood after the woman, that he might cause her to be carried away of the flood. And the serpent cast out of his mouth water as a flood after the woman, that he might cause her to be carried away of the flood.
The dragon who sends the flood is Satan, who moved Herod to attempt to kill Christ at His birth, and it is also pagan Rome as Satan's chief earthly agent in making war on Christ and His people during the first centuries of the Christian era. The water cast out as a flood is a flood of poisonous lies and deception aimed at God's people to mislead those who do not know the truth about them, and truthful testimony is prepared to expose and answer it. The chapter stands with the apocalyptic beasts that arise from the union of church and state, a union that persecutes and crushes those who oppose it.
The verse belongs to the prophecy of 1,260 years of tribulation for God's people in the Dark Ages, from 538 to 1798. The persecution did not continue unabated through the whole period, because the Reformation and the opening of the New World weakened it and gave refuge to the oppressed, fulfilling the statement that the earth helped the woman. The verse belongs to the portrayal of the last great conflict between the obedient and the disobedient, in which there are only two parties on earth, those who stand under the bloodstained banner of Jesus Christ and those who stand under the black banner of rebellion. Those who stand with Christ bear the sign of obedience given in Exodus 31:12-18.
The verse belongs to the prophecies of Revelation 12 to 18 that are being fulfilled now, forming part of the last message of warning that everyone is to hear. That last message of warning comes before the final call in chapter 18 and before the destruction of evil and the triumph of Christ in chapters 19 and following.