Then the third angel poured out his bowl on the rivers and springs, and they became blood.
And I heard the angel who had authority over all water saying, “You are just, O Holy One, who is and who always was, because you have sent these judgments.
Since they shed the blood of your holy people and your prophets, you have given them blood to drink. It is their just reward.”
And I heard a voice from the altar, saying, “Yes, O Lord God, the Almighty, your judgments are true and just.”
References for Revelation 16:7