Revelation 16 (KJV)
4 And the third angel poured out his vial upon the rivers and fountains of waters; and they became blood.
5 And I heard the angel of the waters say, Thou art righteous, O Lord, which art, and wast, and shalt be, because thou hast judged thus.
6 For they have shed the blood of saints and prophets, and thou hast given them blood to drink; for they are worthy.
7 And I heard another out of the altar say, Even so, Lord God Almighty, true and righteous are THY judgments.