Revelation 9:14; Revelation 16:12

Revelation 9:14

14 one saying to the sixth angel who had the trumpet, "Release the four angels who are bound at the great river Euphrates."

Revelation 16:12

12 The sixth angel poured out his bowl on the great river, the Euphrates; and its water was dried up, so that the way would be prepared for the kings from the east .